I would argue the weight issue entirely differently. From everything that is known about seaworthiness and motion comfort, all other things being equal, length is far more important than displacement relative to length. In other words, all other things being roughly equal, then a longer boat of equal displacement will have a more comfortable motion, larger carrying capacity, and be more seaworthy than the shorter boat of equal displacement, plus the longer waterline boat will be faster and easier to handle.
People make a mistake of buying a short boat for its displacement (in other words a heavy boat for its length) and expect it to be more comfortable and seaworthy. While it may have a more comfortable motion than an equal length boat of lighter weight (and I use may because it also may not be more comfortable) the longer boat of equal displacement should really be much more comfortable and should be easier to handle, have greater carrying capacity, smaller fuel usage, and have similar maintenance costs and so on.
At the heart of it, I suggest that you fugure out how much displacement you need to accomplish your goals and then (within reason) look to find a suitable boat of the longest length that has that displacement.