The Solo Loop is a non-starter for me.
Having owned Apple Watch since the first model - and having always worn a Sport Band - I know that:
1. The band will lengthen over time. As others have noted, Apple does state this about the Solo Loop (in tiny print at the bottom of the product page on Apple Store "Strap may increase in length over time."). I don't see the point of buying a fixed length strap that's "designed to provide an ultra-comfortable fit" when you know from the outset that it won't stay the same length. I also suspect it might lengthen much more quickly than the Sport Band, because it's going to get stretched a LOT.
2. My wrist is not one size. Some days (eg when hot, either due to temperature or exercise), I will need the band one hole looser than on other days. If you're measuring yourself for a Solo Loop, keep this in mind. Maybe take a few measurements over time, under different conditions.
3. I don't want the same degree of snugness all the time. Sometimes, it feels irritatingly tight, so I just loosen it. And vice versa. Not an option with the Solo Loop, of course.
So I bought my Series 6 with a new Sport Band instead. I hope to goodness that Apple doesn't discontinue that style, as I feel that the Solo Loop is folly. Time, as always, will tell. And some may love it, which I also fully appreciate.