Personally, just because I'm a little OCD, I don't like how the LS, SR, KA, etc. engines don't fill up the engine bay. The RB does, and looks right at home. Also, personally, I prefer the sound of the RB over the SR. I think I6s are some of the best sounding engines, period. I understand these are both about form, but I prefer form AND function.
BTW, have you weighed your car? I am curious as to how much it weighs, and the F/R percents/bias.