Series 2 all the way.
Looks better inside and out and is more comfortable (seats are quite an improvement).
I owned the first Series 1 NM35 (AWD) and put over 160,000kms on it. Turbo failed and a wheel bearing, but that was pretty much all I can remember going wrong with it.
Very good car and is still doing the rounds. I managed around 9.1km/L on average once I changed the dump & exhaust (although this did increase to 9.6km/L once I had the Fcon in). This was a lot of highway of course, but also daily hills & fun, so not too bad really.
I have ownned a Series 2 PNM35 (AWD) for the past three years and have put around 80,000kms on it. I am currently averaging 8.9km/L (intake, plenum, HFC, V36 exhaust) with the majority being highway travel. The plus side is that the 3.5L Series 2 can be remapped relatively easily and you can always put a series 1 rear diff in if you want slightly better economy on highways.
If you are not going to modify it at all, go with the Series 2. If you want the best performance return under $10k, Series 1 is your car.
I can't help but think that the RWD PM35 would get quite snappy in the wet though (for better or worse).