Braided.
I have both. The solo did not stretch at all, the braided did, significantly.
I have a size 9 which I wore a few years with my S5, now I have a 10 that came with my new S8. The 9 is significantly longer than the 10! Almost 2 or 3mm I would say.
I even went to the Apple store to ask if the 44mm versions were longer than the 45mm - they were not.
However, for me the braided is by far the most comfortable to wear, so I'll continue with it.