I'd say not worth it, put faster rpm and higher static pressure fans on the H50 rad if you don't mind the added noise.
Low 90s is not a temp I'd want to see, is this under LinX load? As you get close to 100 it triggers thermal protection and will throttle or shut down.
Not a massive amount of difference, the radiator on the H70 is about 50% thicker and it has an extra fan.
Add another fan to your H50 in push/pull and have it exhausting out of the case.