I heard of IPSC in late 1980, I guess it was. I and some others started the local club in Austintatious in early 1981. We had some 25 members, including Chip McCormick.
This was before the days of the gamey stuff. No race guns or plastic holsters. 1911s, with good trigger jobs, bevelled mag wells and throat/polish. Better sights, of course. All in all, pretty practical.
So, time marches on as time will and IPSC got gamier and gamier. Some folks wanted to stay more practical and started IDPA.
While I've not seen an IDPA match, from what I understand of the rules it strikes me as easier for an IDPAer to cross-enter an IPSC match than vice versa. Not that it matters.
Seems to me that if your head is into street-tactical, IDPA is probably better. If gun-handling skills and good shooting comprise the overall goal, either is good.
Arguing against either style, or worrying about which is "better" is like arguing between IRL and NASCAR...

, Art