this is a known problem with pure data's portaudio interface. pd is not able to run with low latencies on osx/windoze ... using jack / alsa the situation is better.
Can I infer from this statement that using JACK on OSX is a low-latency option?
it will probably give better latencies on osx than portaudio ... in miller's branch, although i'm not sure, if it's possible to compile pd/jack on osx... (iirc hans has been trying this ... didn't really follow this, though)
in devel, it shouldn't be a big difference if you're running pd with the changed scheduler, that's computing dsp in the audio driver thread.
cheers ... tim