I have 11 URs in JPN verison, here are my 2 cents:
SSR Gohan's decent, but not that strong. STR Goku is way more useful in the long run fyi. DO NOT trade your STR goku for Gohan!!
For the currest SSRs the usefulness is like this STR Goku > SSR PHY Vegeta > SSR Gohan > SSR Piccolo + SSR AGI Goku > SSR TEQ Vegeta
Of course if you rate coolness level SSR Gohan is way up the list, there will be a SSR SSJ2 Gohan later <3
STR Goku is useful for obvious reasons, +50% atk dude, meaning his special will also hit super hard.
SSR gohan is not as useful because later on there will be a bunch of chars that add ki with leader skills or link. He's still pretty good though, but there are a whole handful of better SSR or SSR* (from SR) later. He is not as good as goku because there are limitations to his atk power. Goku still gets +50% when max ki on top of super bonus. Gohan gets none when max ki except for super bonus.
PHY Vegeta is useful because the dmg reduce after hitting someone is really, really useful. especially when you come up against super hard hitting boss with massive hp like mech frieza.
SSR TEQ Vegeta is the ABSOLUTE shittiest SSR in the entire game, hands down. shitty stats and shitty passive. It is pretty much NEVER put in any of my decks in the JPN version.
SSR Piccolo's passive isn't the worst but DEF doesn't really play a big role in the game itself and he has some rather poor stats.
FYI Blue hair God Goku has 8723hp 8250atk 3873def when maxed
SSR TEQ Vegeta has 7757hp 6533atk 4249def with a shitty passive (Even SSR* comes close with that atk)
SSR gohan has 7105hp 7309atk 3299def
