I believe you 100% Toe-Knee.
Yesterday I went to some guitar shops and spent a long time looking at the frets. This issue really bothered me so much - in fact the assistants probably thought I was crazy.
As you say, most of the difference is in the height and dressing of the frets. Some of those metal-ish ESP LTDs have very high frets which are dressed in a sort of unusual pointed way. I noticed the vintage strat-like models have more like traditional Gibson style height and dressing, though I though the actual width seems to be the same for all models.
I also looked at the Ibanez frets, in general they seem to be more or less the same width as ESP, but are less high and more conventionally dressed. As you also said, theres quite a bit of variation in fret types on Ibanez.
Jackson and Charvel had larger frets than Gibson, but not overly. I have one Jackson and hadn't noticed a difference until I carried out this little study.
I also looked on other forums and some other people feel the same as me about the ESP frets, so I'm glad I'm not imagining things.
Anyway, I vaguely fancied an LTD H or MH model, so I am disappointed.