I've had both the 240 and, now, a 940 wagon. The wagon I have is a '93 940. I'd say the 940 is much the better of the two models with a few plus points to the 240. The front brakes and possibly the front suspension of the 240 may be better. All else in the 940 is superior to the 240:

Seats are more comfortable

Driver vision out of the car is better

Handling is better

The back seat fold-down in the '93-'95 940 is vastly more convenient than the 240 or earlier 740 and 940

The design of the electrical system actually looks like it was planned instead
of just growing over the years, It seems more reliable and easier to work on.

The tailgate design is better and doesn't leak!

My 940 has electric windows, electric driver's seat, heated mirrors, mirror positioning from the driver's seat, heated seats, sun roof, tachometer, Electric cooling fan for the engine, a very good R134 AC system, and decent headlights. Fancier models include fog lights. None of these are essential but they are nice to have. Makes the car feel pretty modern.

The layout in the engine compartment is better to work on. They have reversed the positions of the alternator and the power steering pump. The engine is the familiar, reliable, red-block with oil squirters which remove the piston slap problem.

My 940 has the Regina (Bendix) fuel system. This is used by many makes of cars and has been reliable. No expensive AMM to replace.

My main gripe is that the 940 only comes with an automatic, the familiar AW-70 (or maybe AW-71). This has a locking torque converter. The tranny works fine in town and in merging on the freeway if you keep your foot to the floor. However, at speeds of 50 to 65, there isn't as much passing power as I used to get with my '88 240 with the 5-speed tranny downshifted to 4th.

All of that being said, there is a mystique to the 240 wagon that many really like. If I did buy a 240 wagon, I'd go for the '88 with 5-speed or the '93 with the R134 AC system and 5-speed.