Some 739s have a closet/bathroom. If you get the bulkhead in front of the can, you have a lot of room. Your olfactory system will get a treat, too.

All 738s/73Gs have the curtain. If you take the bulkhead on those planes, please don't pull on the F seats to get up or sit down. It's really annoying and since there's a piece of cloth there, I can't shoot you dirty looks.

All 734s have the wall. The wall on the 734 is nice if you're in the aisle. Haven't flown on one of those in a long time, though.