Bigger holes....
Even though .45 minor has a bigger hole, it is purely subjective if a person states "I gained 6 points today....!" Since a single stack .45 with a 10 round mag won't fit the IDPA box, in order to be able to load 10+1, the gun would have to be a double stack frame.....such as an STI Eagle or a Para Ordnance hi-cap. If a person used a single stack with 8+1 for ESP, more often than not, the disadvantage of less rounds may require an unwanted additional reload. An additional reload using a cover garment, may add 2.0 seconds or more from shot to shot, which is comparable to losing -4 points down. If you incur just two extra reloads during the match.....this would be a disadvantage compared to ESP shooters using 9mm at division capacity....
I built and use an STI Eagle 9mm for the ESP div. of IDPA. Due to the tapered design of the magazines and the wider opening of the magwell, I found it is much faster when conducting reloads than any other gun I own. I have a Para Ordnance hi cap, and the design of the mags is less tapered and the reloads are not as fast and smooth as my STI Eagle. I also like the fact I start with one mag loaded with 11 rounds, so I don't have to use a "Barney Bullet!"