On Wednesday, 5 February 2014 at 15:25:27 UTC, Michel Fortin wrote:

In general ARC+GC would release memory faster so you need less memory overall. Less garbage memory blocks floating around might make processor caches more efficients. And less memory pressure means the GC itself runs less often, thus less pauses, and shorter pauses since there is less memory to scan.

Which does not fix a single problem mentioned in embedded/gamedev threads. Difference between "somewhat less" and "reliably constrained" is beyond measure.