I went thru the same thing 2 years ago when I got started.
Sounds like you have a chance to go and see and fondle a number of firearms. All the IPSC guys I know are more than happy to share their view of what is the best gun for the game.
Talk to shooters in all classes, Production, Standard and Open and see what interests you the most.
Could be buy in cost, a caliber that you already reload for, or just one gun that catches your fancy. Sounds like a 1911 fills the bill.
Caliber is a age old question, 9mm is a minor power factor unless you want to crank it up, .40 can be loaded both ways, .45 is the round the whole power factor was based upon.
Magazine capacity is also a concern, 45's are 8 or 9 round? ( do not shoot one some else can clarify this.) If you go to 10 rounders I am not sure if the gun would fit in the required size box. The more rounds the better as some stages require lots of rounds ( max 32)
If you have not found out out about the power factor requirement, time to hit the rule book. In essance the rule is (bullet weight times velocity) has to be equal to or greater a specific number.
Production is a min. of 125, Standard and open are scored as minor 125 or major 170/160.
One consideration is the number of shooters in each class in the club, no fun if you buy a gun that fits in one class and everyone else shoots in another class.
By your avatar I think you are in Sask.? If so most folks are either in Open or Production class.
My choice in the 1911/2011 class would be a name brand gun in .40, this can be loaded down to pussy cat levels or cranked up to make major power factor as well.
Pm me if you want more info, Could be coincidence but I am heading for a open house/ fun match in Prince Albert on Saturday, Is that where you are at?
Ask this question in the action shooting forum for a lot more responses, Lots of good info and great shooters there.
Kim