B34 or B37
I have been on a B37, and I have a B323, which is similar to the B34 although smaller. The only thing I would worry about between going with the B34 and the B37 is docking. I find the extra water line and extra inertia of a bigger boat, make it harder to dock solo. I found this moving from our Catalina 30 to our B323. The B37 has a ton of freeboard, so hoping on and off when docking in one motion is not as straight forward, especially if you are 60+.
The pluses with the B37 is that the v-berth is a really health size, and the boat is a perfect size for two couple cruising. Also, you get a forward facing nav station which is nice. I have always found that somewhere between 32-38 feet is a great size range for coastal cruising, making both of these boats enticing.
I don't know much about performance aspects, but I know that the old 373 wasn't as sprightly as some of the other Beneteau 3 line. I know specifically that a review said that the B323 had no problem keeping up with the 373, which is odd given the 4 feet difference in waterline. From what I can tell, the performance numbers look good for all the 30 somethings in the Beneteau lineup these days.
I hope this helps.
Cheers,
Dan