IF I were you, I'd buy the boat you like and would be comfortable in.
Multiple KK42 could have different bridge clearances due to a number of factors and as was mentioned you can go different routes to get around some bridge clearances,
Champlain Canal, we are on our 8yr Loop, you will need 17' or less to take that. The western Erie Canal, if you want to do that will have you down to 15'5".
Finally, whichever boat you decide on, measure it yourself. We took it in segments, waterline to gunnels to bridge top to radar on the arch. It's pretty close and we measure 17' which gets us under most bridges. That is with the VHF antenna dropped which is easy on our boat.
Trawlers with mast generally need to drop the mast for the trip. Generally, not a big deal.
To me it seems we buy boats like we find women. When you find one with the looks we like, that is usually where we make our move.
Good luck with the search.
m/v Nepidae, Albin 43 Sundeck