I have a P2000 and I have shot various of the SIG Pros over the years. I don't own a SIG Pro, but I do own other SIGs.
The main practical difference with these guns is size. The P2000 is a small feeling gun. The SIG Pro feels "stocky" (thick, but still comfortable) like a 229.
I didn't like my P2000 all that much until I got the extended baseplates for the mags which - stupidly - they don't ship the guns to Canada with. If you buy the gun - order some baseplates from Wolverine or you probably won't like the grip. With the baseplates on the grip is great. It feels similar to the Walther P99 grip. Due to a somewhat unexpected series of events, looking for them in different places, I now have 9 mags - all with the extended baseplates.
The gun is fantastic. I like it more all the time. The balancing seems almost perfect for me. Keep in mind everyone is different. I am a "small gun" guy. My pistols are the SIG 228, 229, 239 and the HK P2000. I don't like pistols that are long off the front. My girlfriend likes Beretta 92/90-two guns. To me those feel long and unwieldy. I'm not saying that is "the way it is", that is just the way is the way it is for me. P2000 I think I can get good control on it firing quickly. Here is a video:
http://www.youtube.com/watch?v=OqOhhqBR63Y
I actually have the target from these 20 rounds (no I am not completely OCP, but I do save some targets

), and it is actually pretty good for the speed of shooting. I'll see if I can find it tonight.
I have a video of me shooting the SP2009 here as well. This is a friend's gun. I think it may have not been clean - the reason why it didn't go into battery when I released the slide. Anyway, it doesn't do that very often:
http://www.youtube.com/watch?v=4NIjnzCECRI&feature=channel_page
The SIG Pro, to my mind, was an attempt to make "SIG Classic" with a polymer frame - and it was a success in my view. Some people bag on those guns, but they are nice, and great value for money. The gun looks and feels a lot like a 228 or 229 on the outside - particularly the outside of the slide. The new SP2022's in Canada have the same nightsights that 229s ship with - which are some of the best on the market IMHO. The gun doesn't have the same balance that a 28 or 29 has, but it is still pretty good. The trigger also seems to be not quite as crisp as a well broken in SIG classic, but it is miles ahead of most of the polymer guns on the market. The trigger is abut the same feel as an HK USP/P2000/P30-type trigger, but the re-set is shorter (strange given the SIG classic re-set, but it is true). I did a side-by-side off-hand accuracy test with a SP2022 and a 229, and got very similar results. That is on the board here somewhere, I just don't feel like looking it up.
If I were going to buy one of these two guns.... SIG Pro is really tempting given the cheap price. If the gun is, or becomes, a parts orphan - that is something to consider... but the price is definitely right. P2000 is 30% more, plus you need those baseplates for it to really come into it's own.
One things with the SIG Pro - they use (what I think of as) as "CZ75-style" barrel and locking mechanism - where the barrel has a loop under it that the slide catch lever fits into:
http://www.brownells.com/aspx/ns/schematics/schemmfg.aspx?schemid=829&m=25&mn=SIGARMS®&model=SP2009+
This is totally different than the "classic" SIGs. Not to sure why they did it that way, but they disassemble more like a CZ than a SIG.
The other thing with the SIG Pro, they have this plastic guide rod with a little plastic "nub" on the end that fits into a little hole on the front of the barrel (part 33 connecting to part 52 on that diagram). Again, not sure why they did it that way, but the little nub thing will wear... and I know of at least one case where it broke off. You can get a stainless steel guide rod, which sounds like a good idea, if someone will ship one to you from the U.S.
The P2000 uses the same "recoil buffer" system that the P30's use. Like the USP's the P2000 inspires a lot of confidence on the wear issues, becuase they don't really seem to wear much. It is a flat (not wound) recoil spring. I guess at some point users should probably replace the spring, and it could be tricky to find one in Canada, but with that buffer in there it should last a long time.
Like the other guys have said... see if you can try both. If one or the other really turns your crank, get it.