The debate that won't end. This topic come up every three weeks or so it seems.
Look the Borg are on paper superior but the Dominion is so vast and powerful it would give the Borg a very tough fight. On paper the Borg should win although if the Borg can't stop Voyager maybe I shouldn't be so quick to make that prediction.
There is 0 indication the Dominion is larger and more powerful than the Federation.
Sure it's ahead of the Feds in some departments, but technologically and how much space they occupy ... they seem to be rather same.
Also the Dominion war was poorly handled in my opinion on-screen.
Unrealistic for Star Trek itself and incredibly dumb-ed down.
So I will repeat it again, if SF had huge problems with the Borg and has to send a fleet to take care of 1 ship, the Dominion would fare the same.
Plus, the Borg can easily stop ramming through extremely powerful (shield draining) tractor beams, and taking into consideration just how massive a single cube is (not to mention the density of it's armor and adaptation capabilities) ... the Dominion would have a tough time just like the Feds did.
Also, numerous Borg ships could activate energy shields around their vessels.
The phased polaron beams would have little effect since the Borg would learn how to adapt (just as the Feds did ... and the Defiant's shields ... which were part of anti-borg systems were capable of stopping Dominions weapons from penetrating them before the crew brought a damaged Jem'Hadar bug to SF for analisys).