I find "most entries" be be a bit of misleading thing- because some comps - like millennium, etc. just have rising star and proficiency entries for every level of bronze- which means some people can enter the 4 levels of bronze singles in their age and below, plus rising star bronze singles at their age and below, plus proficiency, plus open bronze at 3 levels and 2 ages, plus rising star open bronze at 3 levels and 2 ages, plus 6 different 2 dance championships, etc etc.
So sure, there might be twice as many entries, but there's the same amount of people as a smaller comp. and you end up diffusing your competition across all those different options.
To me, the biggest ones that people pay attention to are Ohio, usdc, holiday, millennium, emerald, and embassy.