Super Manga ~ GT >> Super Anime as far as power consistency. Most of the main cast's boosts in GT are somewhat explainable through the power ups they received via headcannon (Goku's lower forms becoming attuned to his SS4 power to explain his constantly rising power, for example). The only problems GT tends to have in it's scaling tend to be more attributed to the supporting cast, and most of them tend to just be from fans looking too far into what isn't that deep. The only power ups in GT I'd view as being as bad as Super's anime are the main trio's increase in power from the Start of GT to the battle on M2 and Pan's Evil Dragon Arc hax, and even they're explainable through Zenkais and Pan's potential (something carried over to Super) respectively.
Super's Manga is pretty consistent with it's scaling up until the Vegeta VS Black fight, though I'd chalk that up to Vegeta training his base and SSJ forms to lessen the difference between his SSB form (like Toriyama said was going to happen with Goku). The only real problem with it's scaling is all the U6 fighters being able to compete with post-God Goku & Vegeta's lower forms, as can Piccolo, though that's not really an inconsistency and mainly just bad writing.