I think you're judging both tournaments on different standards... Name these 8-10 "great" guilds, because I definitely can't think of that many

If we're going to be lax and lump every single VIS side guild, Silver, DoT, and others into the "great" category, then I don't see why we never did the same for SLX, SDE, nVu, BDB, Demon, Pluffy Gang, SNC, Kamei, etc.
It's because everyone sizes up Mixed guilds to Alumni, and we're the best by faaar, whereas iDevice has no team like that

I'd say there are about 4-5 good Mixed guilds, with 32 teams, and maybe 6-7 good iDevice guilds, with 64 teams
Obviously they're going to have a higher number of competitive guilds... They're given a higher number of teams to compete with, that's how math works

If you guys gave us (Alumni) the chance to pick which tournament we'd enter, based on how easy it'd be to win, there's no question we'd enter iDevice (although it'd be boring)
Pretty sure it's the existence of Alumni that causes people to think Mixed is some free win... If that's the case, more iDevice teams would be entering