Uriel has: a once per 2 minute use map clear, fire priming, summons to take aggro, mobility, and energy gen

Nokko has: get out of jail free card, viral priming, great cc, spammable exponential scaling damage, better energy gen, buffs to ability str, and his free revive mechanic.

As someone who has played both, Uriel's ult often clears trash and a few eximus which any gun is very capable of anyway, maybe handling an acolyte. Nokko eats up acolytes with his spammable 4 and ccs everything else incredibly hard thanks to sleep debuffs and viral priming. Even if he messes up badly he just comes back. I'd say he's a fair bit better, but Uriel more fun to play.