There's so many factors to take into account when deciding the minimum size for a boat. Then after all potential factors have been considered, you make a decision, and use the vessel a few times, you'll start wondering how nice would've been if you got the next size up.
Depending on the typical seas you'll be navigating, those 6 miles may be fine rowing on a layer of styrofoam attached to plywood or you may need one of those coastguard vessels that can recover from a 360 flip. Most people needs fall somewhere in between.
Things that were extremely important for me:
-handle around 8-10' seas, we only go out on 3 or less but there's no telling what'll be on the way back.
-space to attach a good ladder, seems like we keep getting older so I want easy access back on board.
-protection from cold and sun, center console's may be sexy but I get cold easily and my husband is a ginger, so the cabin allows me to be warm when all the windows are closed and the oversize top protects my husband from getting burnt.
Less important but nice to have was:
-Ability to hang 2 hammocks or place 2 lounge chairs so we can take naps when seas are flat.
-Rod holders that accept small grills for chilling during the Air Shows, 4th of July or whatever excuse to eat and drink.