I think EPGY is good for a smart student to cover material quickly, with just the right amount of explanation and practice. It has some extra topics (e.g. basic set theory, logic, numbers not in base 10 etc. that are not in most elementary math courses these days). However it seems that what AoPS has, that EPGY doesn't, is deeper problem solving, and this is preferable for the mathiest kids, even if it takes longer to get through the corresponding material.
So one sensible way to do it is to do EPGY from K to 7, the switch over to AoPS for Algebra (I). The higher EPGY courses are much more expensive (with compulsory tutors) but even without that I ultimately prefer AoPS.
We actually got an EPGY subscription before the recent change, so we have the EPGY algebra course, but I am getting DS8 to do Algebra with the AoPS book, and not use the EPGY algebra course (which would have only covered part of what the book does). He'd previously taken K-7 with a k12.com virtual school (which is just average, not for gifted), so I used bits of EPGY K-7 to fill in gaps. In hindsight using EPGY K-7 would have been good.
I don't have the AoPS prealgebra book, but looking at the excerpts, it looks good just like the AoPS books that we do have. The Beast Academy books look like they could be good provided that they appeal to a kid and they are motivated to work through them.
Anyway DS8 is starting AoPS Algebra (book, not course, though it's to be seen whether he'll stay on task with it, which gets back to the question of how well it works for a youngster working through a book, mostly independently).
DD5 just started EPGY math at level K (actually she did K in 2 sittings, so on 1 now), but is not going to go at the pace DS8 did. I can envisage switching to AoPS at algebra, or at prealgebra, or at BA3a. (Another issue with BA is when the books will come out because they've had some delays, but I think gr 4 and 5 should be out in time for DD5, though gr 2 won't be).
