Whichever one you shoot the best and most. I have campaigned a CZ75.
There is a good new shooter briefing at:
http://www.gadpa.com/index.php/ipda/...oter-briefing/
It is clearer than the rule book on most things.
IDPA has a lot of stuff going on besides shooting the gun at targets.
You must be able to load and holster the gun without sweeping bystanders or yourself. This can be hard with an IWB or very close high belt holster.
You must be able to draw the gun from under a concealment garment (vest, jacket, shirt) without getting tangled up.
You must remember and execute the course of fire. This will include moving between points of cover with loaded gun (finger out of trigger guard), it will include shooting on the move, too. There will be use of cover requirements, leaning around high cover, kneeling behind low cover to shoot.
You will have to reload on the clock, maintaining the gun in a safe direction and with finger out of the trigger guard.
You can practice a lot of this stuff dryfire at home, being extra triple check careful to work with an empty gun.
You can search youtube for IDPA videos and see some examples of different courses of fire being shot by people of varying skills.