In reply to Rapsling:
I only have one of the new ones, the smallest. Theoretically the stiffer sling is better for placing one handed above you. Ironically this is probably least useful for the smallest as its quite fiddly trying to place it like that, but I've done it a few times.
I wouldn't replace my old ones with the new ones, but if I was buying for the first time, or my old ones wear out or need replaced, I'll get the new ones.