First off, congratulations to Leah and the other competitors.
I have competed in 6 USPA meets. The only reason I picked that federation was on hamburgerfan's recommendation, and he does not like the USAPL. The USPA is thick on the ground on the West Coast, especially SoCal. It appears to get rather thin West of the Mississippi. So accessibility was a real plus for me when I still lived in SoCal. Illinois typically has 1 meet in the Chicago area each year from my own research.
My own experience of them is that the judging is quite good. They don't suffer shallow depth squats and are death on DL form flaws like foot movement and hitching. Even Paul Horn got called for hitching in the 2015 CA state championships where we both competed.
OTOH, some of the venues were taxing in hot weather. Lotta heat and not much cooling. The 2013 IPL Worlds in Las Vegas were in the Golden Nugget, so A/C was not an issue. But I had one loader misload me 4 times out of 9 lifts during that meet. Only time I saw it or experienced it.
As for the numbers of competitors who show up? I can't compare USAPL numbers because I haven't seen or been to one of their meets. But the 2 CA state meets I have been to had 100+ competitors. YMMV, Tom. But there have never been many old folks competing. Nature of the aging beast, I suppose.
EDIT:
The USPA has been fairly progressive (much as I hate that word) in improving the quality of their federation. They upped requirements for the IPL qualifications, and they added a drug tested division since 2013.