Here is one of the discussions (arguments
http://www.fnzas.org.nz/fishroom/help-w ... highlight=
I ended up going with the full siphon, turned out: silent, no bubbles, constant level, IMO needs a backup pipe to sleep at night.
But anyway back to the sump, the skimmer is the main source of the bubbles not the overflow. So baffles are necessary unless the water after the skimmer is really slow and deep with the return pump at the bottom.