Slower as in the feel of things, or quadrant scores? On their site it states:
In Sapphire 1.0.0, I have disabled the stagefright media player and defaulted back to opencore. This was done because there were reports that opencore produced better quality audio on several applications that stream media over the internet.
Sadly, opencore also takes more time to decode H.264 video, an item that Quadrant uses to determine its score. Thus, the score suffers dramatically due to the use of opencore over stagefright. IT IS IMPORTANT TO NOTE THAT THIS LOW QUADRANT SCORE DOES NOT MEAN THAT THE PHONE RUNS POORLY. OPENCORE vs STAGEFRIGHT WILL ONLY AFFECT MULTIMEDIA PLAYBACK, NOT OVERALL PHONE PERFORMANCE. IT IS A PERFECT EXAMPLE OF WHY A BENCHMARK SCORE SHOULD NOT BE THE END ALL AND BE ALL OF HOW FAST YOUR DEVICE IS.
Regardless, for those who would rather run with stagefright, I have developed an update.zip that can be applied over an install of Sapphire 1.0.0 to change the build.prop to enable the stagefright media player. "
Source builds are based on the source and are (can be) updated nightly or updated with the android repository right before a compile is done. You get the absolute newest code (example...google found a small bug in the phone app or a memory leak with the graphics handling code, etc..and fixed it). Source built roms also have the ability to modify (or replace) the source code before it's compiled allowing them to completely change things (for better or worse).
The others are just unzipping the release (like FRG01B or FRG22) and editing stuff that is in there, maybe adding/removing an app, changing a graphic (theme) or some of the easily editable stuff (build.prop). It's the same version, same code as whatever they unzipped (FRF84B, FRG01B, FRG22, etc..).