I'm going to say no. Bell is probably more talented, but Semi is playing a role that Bell could not have -- defending several different positions while operating as a spot up shooter and hustle guy on the offensive end.
So far, Semi looks to me like a very raw version of Jae Crowder, which is high praise for any first year second round pick. He probably has higher upside defensively, too, given that he's significantly taller (and even more built) than Crowder.