"As far as IDPA, it's a tossup which gun will shoot better. I guess the only concern would be how they fit into the rules."
I would look into this aspect if you want to be competitive in IDPA. If you just want to shoot IDPA for fun it probably won't matter.
I don't know ditty about IDPA but I shoot IPSC a little and I think your choice would have big consequences there. A G34 could shoot production, the SA CZ75 would be in limited and limited 10 where you would compete vs custom 1911's, SVI, STI's etc. You would also be penalized for shooting 9mm in limited and limited 10. The DA/SA CZ75 would fit into production in IPSC.
Now bear in mind this is IPSC and I am sure it is a little different for IDPA (but I think you will run into similar problems). Again, it only applies if you want to be competitive if you just want to shoot for fun it doesn't matter what division you shoot with what pistol.
You could post this in the competition forum and see what people tell you, someone in there must know the divisions for IDPA o hunt them down on the web.