I have a Matched set of CZ Shadow Custom Compentition that I got so I could try my hand at IDPA. I just spent last Saturday running about 9 different ammunition variations through them for basic ballistic testing. I belong to IDPA, IPSC, Steel and a couple of other Shooting organizations, basically because the range I belong to seems to play host to just about every shooting competition event around.
Frankly the rules for each class have a tendency to confuse me sometimes because a pistol that is just fine for certain events in any class may not be acceptable in another class in the same organization. IPDA has about 3 different categories to compete in and as near as I can tell if you want to shot in all three styles then you need three different pistols. I don't know anything about the group you want to compete in so I don't know if they have the same type of rules. I own as I said Custom Competitions, I also own 1 off the shelf Shadow and a Shadow, They all fill my hand, they are all a tad heavy which to me means I have a better change of holding on target. What I do not own is a Shadow Tactical so I can't say what makes it different from the custom.
The only thing I can think to offer as advice is to print out the specs side by side, along with the USPSA competition rule book and see which is the best choice to fit the rules under which you have to compete in. No offence, you probably allready did that, but sometimes the obvious slips past us so I figure it can't hurt to mention it, and just know that I meant no disrespect to you in saying that.