It depends on what type of water you are going in flat bottoms are not very stable V's handle ruff water well and semi v's are very stable for crabbing I would go with your standard center console deep v

Depends on where you are crabbing. I crab out at the mouth of the Columbia River and it can be very rough. I have an 18' deep V that works great.

Edit - It is also an outstanding Salmon Fishing boat

I use a 15' Boston Whaler on LONG ISLAND, good on fuel, very stable, fast, won't sink, perfect for the Bay, it has a "Cathedral Hull"

if you are crabbing you wont the flat for the shallow water. it is very hard to get a boat that works for all times. flat is good for shallow water but does not do good in rough water or wind, you get the feel of being on ice. V bottom is great for ruff water and will give you good control rides not good for shallow water due to the draft over the flat. and the semi-v in my opinion if just a wont to be boat I do not thank it is worth the money. it does not do any job very well.