well i have a 2.4 10v mapped and modded saloon, but also a SW in stock 1.9JTD 16v.
in all honesty, it took me a long time and a good lengthy thread too, to assist in making my own mind up on which motor to buy in the SW, and my finding's s far would be advised as follows.
Dont bother with a 1.9 8v anyway, which if your looking at full facelift model you won't have to worry about, but there is a big tug difference between only 110/115 bhp, and 140/150 bhp for the 16v's and jtdm 1.9's that you should find in the full facelifts like mine.
the 2.4 10v, later models from around 2000 i think, start at 150bhp, not 140bhp, and will map up as far as you like, but in excess of around 185/190 bhp, and much over 300ftlb of torque, you WILL find your clutch will prematurely suffer under the extra torque, as i and many other 5cylinder tuners have done.
the later 20v 2.4 is a stunner, and at around 175bhp to start with, is already a quick thing, and i expect the clutch has been beefed up to suit this, or at least i ruddy hope so, but this motor wasn't used until about 55 plates i believe, so depending on your budget, may or may not be on the shopping list, it wasn't for me sadly!
My 2002 saloon 2.4 10v, is a stonker, i love it, it is so flexible, and i believe the 5 cylinder is a much more refined motor, quieter, smoother, and piped up it does actually make a worthwhile hum.
the 1.9 16v JTDm in my newer 2004 sportwagon, is livelier and free'er to rev, more worthwhile revving as the 16v makes it power and torque peaks higher up the rev range, and with the 6 speed box i managed to find can make for a good sporty drive aswell as great cruiser at bugger all revs.
Its a stock motor at the moment, so i am missing a bit of the 2.4's tug, but i have pipe and map work already planned for it, so it will soon pep up to around the 2.4's level of tune, but should be livelier with it.
i gather the clutch on the 16v's will handle 180/185 bhp levels without mod, whereas in the 2.4 i had to fit the CG Motorsport HD clutch, which is no biggie really, and i may do it again as a matter of course in my SW just to be safe.
so my recomendation would be a 2.4 20v if your budget allows, a 1.9jtdm 16v, 140 or 150bhp, (they will both map up to similar levels anyway) but with a six speed box, then pipe and map, or a 2.4 10v with pipe and map, but you will need to hd clutch the thing aswell if you're mapping for big numbers.
they are all good, which doesn't help decide i know, and i love the new SW i have, and the only negative i would say is that the 1.9 16v definitely has that diesel clatter to it around town, the 2.4 sounds a smoother tighter motor altogether.
good luck, happy shopping,