Mods - if this belongs in "beyond 223" please move.

Hi all,
No this is not another AR vs AK / 45 vs 9mm thread. I'd like to get a bit of education on the comparitive differences of a 9mm vs .45acp AR for fun shooting and HD.

I understand 9mm is about 300fps faster and flatter trajectory than .45. I understand the differences between the calibers in terms of wound profiles (I work in an ER - seen it first hand) and price of rounds. I see lots of 9mm AR platforms but very few in 45. Is it really all about the the 45s lesser performance at 100 yards and over? What are the pros and cons here?

This will help me with my next AR purchase. Thanks in advance.