Re: J or Bene?
Friends have a B First 310, they are quite happy with it having moved up from a rather spartan Martin 242.
I think what you'll find in general with the Benes is that they cram a lot of interior into their hulls - sometimes to the point of squishing everything into the ends.. leaving V berths so narrow and pointed at the foot as to be confining, and even the aft quarters may feel tight - although coming from a TBird it will seem palatial, I suppose.
The J34C won't have as many berths but what it does have will be more properly sized. Also the wood slat cockpits on the Benes will be a constant maintenance issue unless you let it go grey. The J is probably a substantially larger boat side by side.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)