To throw my two pennies is. I am not sure Gomez has looked better than Holgate. Both of them look talented players but both have mistakes in them. Holgate's get punished more brutally because he's in a poorer team but I actually think he's made less mistakes than Gomez and has actually had far more experience at CB than him.
The Alexander Arnold/Kenny one is more clear cut. It's funny as this time 15 months ago, you watched both lads at reserve level, both playing right back and there was no doubt who the superior player was. In the reserve derby Kenny was better. For the entirety of that season he was the stand out right back in the youth league. He'd had some first team experience and did very well. He then won the World Cup for the under 20's (a squad TAA didn't make) and was one of the best players at the tournament. IF you'd have asked anyone at that moment which lad puts a late run to get into the England squad 99 out of 100 say Kenny.
Both lads get opportunities because of other lads injuries but without doubt Arnold seized his chance more than Kenny. It may be Arnold over performed and comes back down to earth a bit this season (a bit like Davies, who over performed then resorted to mean). I do think though, Arnold is a much better athlete than Kenny. He's quicker and stronger. He has great technique, but Kenny's technique is good enough for that to be competitive (he delivered crosses well).
I think thats the big thing for me with Kenny. I think he lacks a yard of pace. Everything else in his game is very good. However I think it's hard to be 5 ft 9/10 (even with a good spring) and lack pace in that position. You either need to be taller and more competent defensively or quicker. I am hoping part of this was down to Allardyce/Koeman/The chaos at the club. That they stifled him. In that defence he had always looked quick and attacking as a full back for the 23's and England youth teams so there may be something in it. However there is another part of me that thinks pace is rarely stifled, you are either quick or not. We will see I suppose.
Kenny can be a solid defender and might surprise a few by getting forward more but thats my one concern. It's what differentiates Arnold from his presently. I think Kenny is the better defender and knows the position better, a better tackler, better in the air. However Arnold goes past players and that skill has elevated him so far.