I used to use Pete's Dsound Driver, but after the new Andy's version (0.16) i have changed.
This new version improved the quality for Square's games and others, making them sound MUCH better. Definitely, it's my favorite sound plugin.
I haven't tested with many games yet, but i haven't had any problems until now.
It really depends on the game you're playing. For example, MGS runs great with Pete's DSound 1.11, while other games don't. That's why epsxecutor is useful, for you to configure each game with its proper plugins. Personally, I use Iori's SPU for most games.
Indeed it would depend on the game....and the emulator..
Andy's SPU is a join effort plugin by authors Andy, Iori, Null2, and more...It is truly remarkable and works well with most games. It does not work however with ADRIpsx and possibly PSinex..
In some games for example MTV Music Generator..both Pete's and Andy, and even Iori's plugin could not handle some of the sound effects. So we used Null2's Audiomixer or Prodigy...keep in mid this game has high demand on sound..and low demand on graphics..
So as the others stated..the plugin depends on the game..and the emulator being used... Our guess is that Andy's plugin will be the best selection for EPSXE use...