The five logic 8 compressor types imo are:
Class A_R = Rupert Neve's vintage 33609 compressor
Class A_U = Vari-MU, where U represents symbol for greek letter pronounced "MU" ie. VARI-MU (famous Vari-MU compressor - Fairchild 670)
U doesn't stand for UREI but stands for "MU" in Vari-MU compression.
Opto - LA2A (teletronix)
FET - 1176 (Urei)
VCA - SSL bus compressor or Dbx 160
Plantinum - Clean digital compressor. (no harmonic generation)
With these 5 types, logic 8 compressor gives a selected overview of past famous compressors.
I believe UAD also has the same emulations of Neve 33609, Fairchild 670 (vari-mu), LA2A, 1176, VCA VU (dbx 160)
It only seems logical that great companies like apple and UAD, Waves, URS, MOTU, etc. offer us exactly the same/similar things....doesn't it?
Logic 8's compressor looks very versatile and offers exactly what UAD offers but cost much less. With a modern 8 core G5, you're left with ooooodles of CPU power.
Also note that logic states that it uses 64 bit precision "where required". My guess is that Logic 8's compressor Internal audio resolution is indeed 64-bit precision where it's required. and that puts it in the same resolution as WAVES RENcomp (native version).
Why doesn't Logic just bite the bullet and re-state the obvious so we can all stop guessing. Not a very good way to market a product when you're strengths are not confirmed/agreed/known by all.