Having driven both, I would go for the R35. It's an enormous car, but the way it moves...you won't feel that at all. Go for a 2012 and up model...cosmetic changes look much better.
Sure, the R8 is nice, but to me it's just a glorified Audi TT. The R35 has the whole GTR heritage behind it.
Just my 2 cents.
that r8 turns heads almost as if it was a lambo but that R35 is rare to see also, I love the interior also, i have a appointment to see them both saturday.