[Hortence:The Muleface Mod]

I play and love both. They really have a different feel to them, so they're decent to trade off when one gets stale.

For the longest time I also always felt like Pop'n was way easier to time and comprehend, but apparently a lot of people feel the opposite way.

IIDX also doesn't have as much focus on notechart structure, at least from a player's perspective, because the use of Random won't ever make a song physically impossible. If you use your elbows to play Pop'n you can sort of use Random, but it actually makes the game much harder in mose cases. (Notable exception being Classic 4.)