I mean I definitely give Brian kudos for being a rather versatile performer, but yeah, his Telly could really get on my nerves. Again, it was especially when Telly would get really whiney about something, like Episode 1709 when he thinks Big Bird won't want to be his friend anymore since he met Rusty.
Marty's Telly on the other hand can be like that one thespian in drama class who always has to really ham it up during their performances: if he's happy, he's so **** happy; if he's mad, he's like one of 12 angry men; and if he's worried, he's like a doomsday prophet on the verge of a total nervous breakdown.