Black Hole: PUBS
Section X: IMPS
That's my experience as well. The difference in BH is mostly down to End of Torvix taking a little longer than Chasing the Shadow. Ilum on the pub side is mostly hurt by the stupid shield gathering quest. If they changed that to a 100% drop rate it would be fine. On Belsavis you have to travel a little more between quest nodes on the pub side, since the quest givers are all spread out.
The balance for the most part is not too bad, though. Except for Section X. It takes much, much longer on the republic side than on the imp side, thanks to two quests that take a hellava long time to solo, and require that you fight through most of the mobs within two moderately large dungeons.