I've got the nimbus 15. I absolutely love them. My feet are a bit sensitive so I like the extra cushioning. I have to wear orthotics and so I need a neutral shoe like the nimbus. I haven't tried the W1080v3, though, so I can't make a comparison.
My best advice is to try them both on, preferably at the same time and somewhere that can look at your gait whilst you're trying them if possible.
Blood test done and visit to Doctor over. The results were as expected - my dose ws too high and all these symptoms were related to that. I'm expecting to lose the overdose symptoms in about 3 weeks and go back for another blood test after 6 weeks.
I chose a doctor with a particular interest in thyroid problems and she told me that my exercise level will definitely be affecting my thyroid levels.I didn't ask her about varying the dose according to exercise levels, but I'm going to keep a record of symptom chjanges and see if I can spot a relationship myself. I guess that is going to take quite some time!
Thanks for everyone's comments and I hope this discussion is useful to many people.