FYI what you linked me too is VERY old, gigabyte had more than 2 line ups here they are:
EX58 (original, UD3R and UD5 VERY different)
X58A-(only 3 initial boards UD3R, UD5 and UD7, Identical layout and SLI)
X58A Rev 2.0(Added UD9 rev 1.0, as well as X58A-USB3, UD3R and UD5 still identical layout)
OK so I just looked up both manuals and general schematic, and well there is no difference in SLI capability. both have the same instructions. What the guy should have said the difference between UD3R and UD5 are power phases, UD5 has 4 more, Cooling, SLI supports IS the same. Google it, they don't do SLI software anymore, fi you graphics card has the physical adapter, then you don't do software SLI. That guy was probably just trying to get you to buy the UD5.
Differences That I can see:
4+ phases on UD5
Diagnostic POST LED Display(tells you exactly what part of post failed when OCing)
Everything else like chip placement and traces are pretty DAMN similar, look at up-close shots, like the UD5 rev 2.0 review in my sig that I did, its all you need to know about these boards, you should give it a read. If you wanna wait for sandy Bridge i have A review on the P67A-UD7 in my sig as well that I just did.
Edited by Sin0822 - 12/17/10 at 12:12pm