I'm no expert in this, but I think reference counting is also more predictable (latency wise) making it superior memory management method for real time applications. GC performance depends on the GC algorithm, but I never recall seeing a GC that was conclusively proven to be faster than reference counting. One thing GC does have that reference counting does not is the ability to handle circular references though.
The performance of reference counting is pretty much constant with respect to the amount of available memory. Conversely, garbage collectors will improve steadily as you add more memory (interesting special case when the amount of memory is infinite). So, if GC's aren't ahead right now, they will eventually be.