The best boat for cruising the Inside Passage to S.E. Alaska may be the one that you currently own. All kinds of vessels safely round trip to Alaska each summer from sailing vessels to power boats including both planing hull and trawler style of vessels. Because most of the trip to S.E. Alaska is in protected waters, having an off-shore capable boat is not necessary to safely and comfortably take this cruise. Having said this, however, there are a couple of issues that may improve ones' trip...
The type of vessel that I would personally recommend is a displacement hull power boat followed by a semi-displacement vessel then either a planing hull power boat or a sailing vessel-especially one with a pilothouse. Why? First of all a round trip to Alaska will entail many, many days of cruising in the rain. Having a vessel that provides a steering helm that is protected from the weather is worthy of consideration. Either an enclosed pilothouse such as those available on most trawlers or an enclosed upper helm station will provide comfort. A second consideration is visibility. A pilothouse having a glass windshield with wipers is ideal with the common strataglass enclosures on many flybridges being a poor second choice. If your current vessel has a bimini cover only, you will quickly learn that the vessel's forward motion will bring rain (and dense fog) as well as cold air under the cover. Fully enclosing the upper helm station is an option but the strataglass windows in heavy rain are very difficult to see through, however the full enclosure will keep some of the cold and wetness out. Some folks plan to steer from their upper helm station in good weather and then go to their lower helm station when it is rainy, cold or in fog conditions. The problem with this option is two-fold. One: The best visibility on any vessel is from on high. Trying to view oncoming waves, debris in the water, much less the scenery, is typically difficult from a lower helm station, compared to a helm station located higher on the vessel. Two: Many boat owners don't have ALL their electronic equipment located in both locations. I recommend that you seriously consider having your navigational equipment, radar, VHF radio and depth finders located at your primary steering station, namely from the upper helm station when possible.
From the San Juan Islands of Washington State north, relying on wind for propulsion is rarely available. Either there is not enough wind or based on the desired heading, the direction of the wind is not reliable. The second factor, as mentioned above, deals with visibility and comfort issues on many sailing vessels. At the least, having a bimini is of value, but it needs to provide cover for the helm station. Otherwise, the helmsman will be spending hours at a time standing or sitting in the cold exposed to a nominal amount of wind, but saturated with rain. Not only will the helmsman be cold and wet, but the forward visibility will be impaired. Also, the viewing of the onboard radar and navigational program may be poor while underway. Finally, how often will the sailboat crew members be likely to maintain watch with the helmsman outside when it is toasty warm and comfortable inside-especially for hours at a time? Sure, you can wear high quality rain slickers, boots, a hat and gloves, but if you are outside in the weather, how does this picture compare with being out of the rain?
In spite of the above comments and observations, a trip along the Inside Passage, is well worth whatever discomfort you encounter along the way!
In case you are wondering about my personal vessel, let me fill you in... Our vessel for the past 20 plus years is a 32' twin screw Bayliner powerboat that was built in 1985. In that era the vessel was not designed to get up on plane. In fact, we travel at under 7 knots while underway. Our fuel burn compared to a planing hull of a similar length is substantially less and we get to wherever we desire to go. Faster boats will arrive at a destination quicker than we will, but we eventually arrive at our destination, too. Having had a 28' planing hull vessel previously, I would comment that it was a nerve-racking experience formerly when cruising at better than 20 knots across the water, uncomfortable in waves of 3 feet or larger, and didn't afford the amenities of our present vessel.
Immediately after purchasing our present boat we fully enclosed the upper helm station with a high quality strataglass product to make sure that our visibility in any direction was good. The cover of the helm station was canvas. What we discovered was that seagulls were fond of landing on the canvas cover leaving their white stain behind which eventually leached through to the underside of the canvas. Thus every few years we needed to re-cover the helm station. In sunny weather we found that the enclosed flybridge was a greenhouse and without having zippered sections, especially front and rear, we'd have roasted. Even without sunshine, the enclosed flybridge is typically warmer than the outside air. When the upper helm station was enclosed we relocated the vessel's radar above. We also added another depth finder and second VHF radio to the upper helm station, too. Our navigational software is via a computer with a 9"x14.5" screen connected to a GPS puck. When through cruising for the day we disconnect the computer from the dedicated inverter located at the upper helm station and bring it below where we can re-connect to an inverter in the salon to plan the next day's route. At night the computer is put away in its mostly air-tight traveling bag. We do 100% of our cruising from the upper helm station and made a couple of significant changes to it over the years. I built a hard top cover for the helm station, built an eyebrow and extended it in front of the helm station, then built a glass window across the front of the helm station (which matches the angle of the glass windows below). I then added windshield wipers to the glass windows ensuring great forward visibility regardless of inclement weather. What we learned in our numerous trip to S.E. Alaska and/or to northern British Columbia is that we would rather look down on waves and swells from the upper helm station than we would look upwards from the lower station. This brings me to another concern about the 'ideal' cruising vessel-namely its size...
I would suggest that a larger vessel, in and of itself, will be safer and more comfortable than a smaller one. Yet, except for just a couple of places between Washington State and S.E. Alaska, most of the distance is in protected, inside waters. The notable exceptions include the Strait of Georgia, Queen Charlotte Sound and Dixon Entrance. Thus, virtually any well found vessel can safely round trip to Alaska along the Inside Passage. A larger vessel besides being roomier within, typically has more amenities so that the larger size is of itself more comfortable. Our vessel, for instance, at 32' has a 3 burner (propane) stove and oven. Our former 28' vessel had a two burner alcohol stove without an oven. Home made bread fresh from the oven is sure a treat! A roomier stateroom and spacious salon are pluses as well.
Let's consider size of vessel and size of swells for a moment. Assume that a 30' vessel comfortably handles a 3' swell, a 40' vessel handles a 4' swell, 50' vessel-a 5' swell. I am not aware of a universal formula such that for every 10' of vessel you can add 1' of swell comfort, but it makes sense that this is true. A friend of mine in his 60' boat thinks nothing of cruising in small craft advisory winds while I hide for another day in my safe cove. To conclude, a larger vessel can take larger seas in comfort and due to its larger size affords a greater degree of comfort. Yet, there is such a thing as too large a vessel, right? There are numerous anchorages that our 32' boat can navigate in comfort that would preclude anchoring of a 60' vessel. One of the anchorages in my mind has a very tight corner that needs to be made upon entry and others are so small that a larger vessel wouldn't have enough swinging room when anchored.
To conclude, whatever size or type of vessel that you currently own, make it as sound a boat as you can and head north. Don't wait! If you currently don't have a vessel I hope that the comments above will provide you with some ideas about what your 'ideal boat' should be.