My information is a bit out of date aparantly (of course my Limited Gun hasn't been out of it's case in 10yrs probally). I apologize for opening my mouth when I should have know every organization moves along with the times.
I went to IPSC's website and found they have the classes listed out now as:
Open, Standard, Modified, Prouduction, Revolver Standard.
They have a list of rules, all the powerfactors, min calibers ect here.
http://www.ipsc.org/pdf/RulesHandgun.pdf
When I still shot IPSC, 9X19 usually wouldn't make the power factor (and I had to hand load the crap out .38supers to do so) to be competitive but looks like they have adjusted some of the classes and things over the past few years to more closely resemble what people actually carry for self defense these days.
I do rember a few Glock shooters comming in around the mid 1990's but I had no idea they were as popular as they are now. I guess the wide spread acceptance of the 9X19 and the addition of a "stock gun" type class has helped spurn that along.
I don't see a Limited class anymore ... If Prouduction is going to be your bag buy what YOU shoot better, as with both being 9mm there is no difference in power. Speed and accuracy is going to depend on your ability.
If your going for the Modified class you are going to have to have something custom built to be competitive. And that entials a 1911 or a Glock (in at least .40 cal, It would be much harder to be competitive shooting a minor caliber) as I don't know of any good smiths invested in heavily modifying M&P's. Not to say an M&P couldn't be done but why row against the current...
R/S
Will