sojournerphoto
Veteran
I've had both ultron and colour skopar. I'd choose the skopar, primarily because it's smaller. I suspect it's slightly sharper too, but that is not important. Both draw nicely, even though they're not the same.
I'll some pictures if I can find them.
Ultron 1.7/35 on Ektar 100
Color-Skopar 2.5/35 probably on Portra iirc
The suggestion of a non vf body and 15 or 25 is good too