I have been using Takumars with both – NEX 5N and NEX 7. Any of those cameras will do well with Takumars, but for the most exciting results you might consider full frame.
Lenses originally designed for full frame, especially legacy ones, will benefit of similar projection size, rendering image similar to what they were designed for.
On APS-C sensor, part of the lens projection (yes, that is worst part of the image) will be cropped of course, but it depends on you if you like it that way.
From the technical point of view, there are not many differences between NEX 5 (N) and NEX 7 in terms of critical corner performance at wide open apertures with this lens.
Hope it helps,