Owned an LS4 and flown quite a few hours in the 7. Both are very pleasant to fly. The 7 has less cockpit room, but not as tight as Discus/Ventus "A" fuselages.
The 7 has a tilt-up instrument panel which certainly the early 4s didn't (don't know about the b). Believe the winglet mod on the LS7 improved the low speed handling, although I didn't dislike it with original tips. The LS7WL is the only version of the 7 that you can get a 3000-hour life extension for.
As previously noted, LS4 and 4a require 4x L'Hotellier fittings be connected and the LS Sleeve used. The 4b has essentially the same hookups as 6c, 7, 8 and 10.
Must agree the condition, trailer and instruments make a bigger difference.
Jim