There is a difference, which is Franken did these deeds as a sitting Senator.
True, some of them (not the photo with Weeden).
Which means they could have a formal ethics investigation of Franken if they want to. And, they could have one of Moore, although the case would be flawed, because as you say, anything he MAY have done occurred before he entered (hope, hope) the Senate.
But, I don’t think that this difference is what’s driving the calls for Franken’s resignation.