Why don't you try it? But my experience says headphones always sound best because they deliver the most comprehensive frequency range to your ears AND separate stereo channels. But the degree to which sounds get worse via PA varies with the type of sound and obviously also with the manufacturer. I've often heard that Yamaha somehow manages to keep sounds crisp and clear via speakers. My experience is also, e.g. for pianos, the more realistic a piano sample sounds, the more difficult it gets to keep it crisp and clear via PA.