[Rohansi]

> How are we measuring "worst possible" here?

The garbage collectors used by both .NET and Mono (since 2013) are precise, concurrent, and compacting. They know exactly what memory locations are GC references, scans them while the game is still running, and moves objects in memory to fix fragmentation. Pause times are kept short because heavy work is done on a background that.

Unity's GC is conservative and incremental. It does not know what addresses are GC references so it has to scan everything that could be a GC reference. It's incremental which is nice but means you're expected to trade a few milliseconds of your frame budget for the GC to run. Being conservative means a chunk of your budget is spent scanning memory locations that aren't GC references. By default it uses the time spent waiting for vsync to run but not everyone plays with vsync enabled and lower spec systems have less room there so they end up running worse.