Having worked with each, I'd say that between Peco and Micro Engineering track:
- Peco is far and clear more durable, especially when laying track
- ME is far more accurate looking as the turnouts are longer and the rails more prototypical looking
I used ME track on my own On30 layout and there were times it was driving me nuts, especially with the turnouts as they're insanely fragile. But now everything's in place (after replacing two turnouts) I must admit it does look really good.