ALSA as the only thing running on your system does. But if your game supports ALSA then it can plug into ALSA which plugs into PulseAudio and you still get all the benefits of PulseAudio.
I always uninstall pulseaudio as the first thing I do on my Linux box.
I have always noticed a latency between the time that a sound is supposed to be played and when it is actually played with pulse. This doesn't matter so much when listening to an MP3 or whatever but if you are trying to use a sequencer or play a game it becomes a deal breaker.
You can connect to a remote audio server. I've used this feature to output sound from my laptop through my desk speakers even when my laptop is unplugged from its docking station.
