In my opinion, there's no straightforward "best" ROM. It all depends on what you want to get out of your phone, really. As Mercury stated, the three main Gingerbread (2.3.5) ROMs are DroidSmith, WarpOEM, and HaloBean.
Jimsmith80's DroidSmith (currently 1.7.3): Probably the fastest ROM here, pulls average benchmarks of around 7500 (AnTuTu). As the author states, it's intended to be as stable (and fast) as possible, with very little pre-installed software.
Mercury0x000d's WarpOEM (currently 2.70): Slower than DroidSmith, but not by much, with average benchmarks around 6000 (AnTuTu). This ROM is designed around a unified "Warp" theme and performance. This ROM provides a bit more pre-installed software.
Skinnyjeans21's HaloBean (currently 8): Averages around 3000 in benchmarks (Quadrant). This ROM is aimed at reproducing the look and feel of Android's JellyBean UI, and is very extensively themed. There's not much additional software as of the current release.
This is hardly all the information about these ROMs, you should read up on each of them. That being said, HaloBean is my current daily driver, prior to that it was the (now discontinued) Shinjitsu ROM.
DM47021 is also working on CM10 (JellyBean 4.1.2) and progress is coming along nicely for it (currently Beta 1.1).
This is not in any way intended to make any ROM sound better or worse than any other. All of the authors put in a huge amount of effort and work to make their ROMs the best they can be. Hope this helps you with your decision.