They are very similar, made by the same company. Both are high end fancy surfaces that look great and last a long time.
PebbleTec uses larger pebbles and has a rougher texture. PebbleSheen uses smaller pebbles and has a smoother texture. I think PebbleTec looks better, but that is something of a personal taste issue. PebbleTec is definitely harder on your feet, which really bothers some people though most people don't mind it too much.