Go with the bimmer. I just traded in my 1999 9-3 for a 2004 330Ci. The Viggen is probably the best Saab ever made, but it still has its problems. For starters, you'll be dealing with torque steer--inevitable with high-powered FWD cars. The Viggen is pretty notorious for this, and if you still decide to go with it, I'd look into getting the Viggen Rescue Kit (just google it). This will help with the TS and also give you some additional handling gains. Some common problems:
1. SID (Saab Information Display) Failure/Dead Pixels
Just about every Saab 9-3 from that generation will see this at least once. Mine died at 26000 miles and was going again at 78000, just before I traded in 2 weeks ago. If you check the car out, make sure you hit the up and down arrows to page through the screens to look for any dead pixels. A replacement SID will cost around $400.
2. Super-loud Creak from Undercarriage
Oddly enough, this is NORMAL. This sound is extremely disturbing and the first time you hear it, it'll sound like you seriously broke something somewhere under the car. Just about EVERY 9-3 has this issue and it comes from somewhere in the strut arm or strut assembly itself. Unfortunately, this sound only shows up in sub-40 degree weather, so you'll likely not get a chance to hear it in this weather.
3. Strut tower mounts
They suck. Mine were falling apart after just 50,XXX miles. Various Saab mechanics told me that this is a common issue, so make sure you get a tech to check it out for you.
4. Exterior trim fading/cracking
Again, pretty common to see this happening. Make sure you check out all the exterior plastic trim.
RATTLES
This is really the most annoying aspect of these cars. Bimmer owners, especially coupe/cab owners, complain about rattles and squeaks. Well, this is nothing compared to Saabs. I nicknamed mine The Rattlesnake.
Maintenance and repair costs are about the same between Saabs and BMWs. In some cases, Saab parts can cost quite a bit more, so I think that's a wash.
Don't get me wrong. I don't hate Saabs. But I'm fully aware of their pitfalls. They're fun cars to drive and the Viggen is the best Saab by a mile. But the 325Ci is just gonna be more solid and better all around. You're in AZ--there's no reason to get a FWD car, even if it is a Viggen. Good luck and I hope this info helps.
p.s. You can get a lot more info, and probably a lot of pro-Viggen opinions from Saabnet.com.