I shoot a slightly tweaked CZ SP01 Shadow in 3Gun and IDPA (some debate if its legal for IDPA my understanding it is since they increased the weight limit) and I am planning on shooting it in IPSC (have done black badge course haven't got out to a match yet). My opinion best gun out there for the money to shoot multiple disciplines. I also shoot a 1911 and have quite of bit of trigger time on sig 226 and variants and some time trigger time on Glock and M&P. Of the two disciplines you mentioned, IPSC has the most restrictive rules with regards to what your allowed to shoot in particular if you want to shoot production class and also will be the most demanding on your skills. I would focus on that decide what gun you want to shoot that with, any pistol that will work well for the IPSC division you want to shoot in will also work just fine for 3Gun (Unless you decided to jump into a full blown open gun). In order guns I would consider SPO1 Shadow, M&P Pro, Glock 17 other CZ 75 variants (if you want to shoot production ensure its a DA/SA) CZ P09.
