UOSteam I think is a bit newer, but both are unsupported by their devs at this point as far as I know.
UOSteam has a bit more powerful macro interface. But on the other hand it cannot handle the old-style gumps that we have here in the macros. Razor also has a bit better dressing mechanics as it removes conflicting items before trying to equip the new ones. Other small stuff like that.
Some ppl have a white flash flicker in their client when running Razor, maybe from using compatibility mode, which doesn’t seem to happen in UOSteam.
I personally have both installed for different situations, but plan on using UOSteam when not afk macroing.