Doesn't matter to me. I don't like turbo engines. Plus yours in particular is remapped so not a true comparison of each model.
A GTR Nissan will "embarrass" a 997 GT3 but I know which one I'd rather own and it ain't the Nissan (great car that it is). A remapped TTRS would "embarrass" an R8 but given a choice between the two not many would be asking for the TT's keys.
I was playing devils advocate though - the M3 for a grand more with the same mileage represents better value for money IMO than that 35iS. But, the E93M is too heavy and I personally would always choose a coupe over cabriolet M3 but if you like roof off motoring it would be a difficult choice for a lot of people given the small difference in price. The 35iS is a nice car but I would've thought 25-27k for a low mileage example is nearer the mark. There's no way even with that mileage, that the car has retained 70% of its value after 3 years.