My experiences and opinions, may or may not not be typical. DYOR.
M&B Hyperflex 10 has more cores in centre, so far rotator loop no problems, M&B Ultraflex 10 seems equally good. Ultraflex 13 also has big number of centre cores and the more recent batches I have bought meet published specifications, There were early batches that seemed not to meet spec (or perhaps spec improved latterly) in all cases though, despite some rough treatment at times on temporary set ups, examination of lengths cut have showed no foil radial cracking that can happen on Ecoflex and W103. Of course W103 is not designed for flexing, for permanent installations, it is a very good choice for low loss runs up to and including 23 cm, just never flex or roll up.
Currently 20 m of M&B Ultraflex 13 in use on 23 cm, just one length. including around rotator on scam 12 pump up, much abused with the ups and downs and getting caught on the shrubs/ mast legs. So far unable to detect spec changes, when checking with the power in/out method. The Ultraflex connectors are solderless for 13 and some on 10 as well. The connectors (provided you pay a proper price that is, some poor copies out there), are excellent quality. The M&B PL259 plugs for Ultraflex 10 are quite excellent, by far the best connector I have used, all of the M&B connectors make excellent and permanent connections to the screen/braid and are highly water resistant.
A short length of RG213, especially the double screened versions, will still be the best "fit and forget" option for a rotator loop, especially if your masts have to be professionally rigged, removes any anxiety about foil cracking failure.
I remember the Camb Hams group repeatedly reporting problems with Ecopflex range on their portable activities, they changed to something else but I forget what it was, with no further problems IIRR.