I'm not a 1911 shooter, but if I were to pick an IDPA gun, I'd like it to be able to cross over to USPSA as well. That effectively eliminates the 9mm 1911 then. For IDPA ESP, I'd either go with a striker-fired 9mm (Glock, M&P or XD) so I could shoot USPSA Production, or a double-stack 1911 in .40S&W (e.g. STI Eagle) so I could shoot USPSA Limited.
A .45acp 1911 can be shot in IDPA CDP as well as USPSA Single Stack, so between a 9mm and .45ACP 1911, I'd opt for the latter. A 9mm 1911 is cool, but it simply has too little general utility for my taste. YMMV.