I’d rather not have the Senate go after the Bidens. It is too obviously political. Let the Ukrainians investigate them all they want. Of course Trump will get blamed for that also, but who cares? I’m sick of bloviating Congressman and their laughable investigations. (big expectations Gowdy et al).
I see the point of congressional investigations as entirely political. That's the point of conducting them, to dirty up the political opponents. That and to congratulate the various federal departments and thank them for their service.
I suppose another purpose is to mislead the public. See the investigations into government snooping, and the promises that this would stop.