I'll be comparing quaver to osu!mania since those are the two I play
Pros:

• Better mod customization (eg. speed in increments of 0.1x vs dt/nc)
  
• Support for importing mania maps (and other similar games)
  
• Gameplay feels better (inputs feel nicer, you can add a line on beat for reading, etc.)

Cons:

• UI is sometimes finicky
  
• Ranked selection is not that good imo, but idc about rank that much so less of a point
  
• Only 4k and 7k, while mania supports 2-9k

Overall, holds up pretty well to mania

I'll be comparing quaver to osu!mania since those are the two I play Pros: [list] [*] Better mod customization (eg. speed in increments of 0.1x vs dt/nc) [*] Support for importing mania maps (and other similar games) [*] Gameplay feels better (inputs feel nicer, you can add a line on beat for reading, etc.) [/list] Cons: [list] [*] UI is sometimes finicky [*] Ranked selection is not that good imo, but idc about rank that much so less of a point [*] Only 4k and 7k, while mania supports 2-9k [/list] Overall, holds up pretty well to mania