If Hilary would have won, OH and Pa senators would have been on the hot seat. But, this is a Trump midterm and Brown and Casey are undefeatable.
I don't think that's true at all. I think they're both vulnerable, but whether they keep their seat or not depends on a lot of things (Trump's performance, who their opponent is and many others). My guess is that Casey is more vulnerable that Brown.
I totally agree that it depends on a lot of things and that making predictions at this point in time is useless (which doesn't seem to be the case among other posters here), but I really doubt Brown is less vulnerable than Casey. At the end of day, OH is simply more Republican than PA.
And Casey won in 2012 by a wider margin than Brown. I'd be surprised if Casey lost; I wouldn't be surprised if Brown lost.
I agree. Casey is more moderate and a better fit for his less Republican state.