I my mind the choice of a R8 could only ever be made against a 911 anyway.
As they are both run if the mill cars from run of the mill manufactures, why not save a huge lump and buy a GTR Nissan then? far better bang for your buck. If your watching costs.
The 458 is is a different class.
But perhaps I am biased?
458 coupe normale, California T, Speciale A, 458 GT3, FF Maserati Ghibli diesel!
on way in 2015: La F, and 488, 2016 488 spider