I would take Hill over Keenum but its a bit of a toss up. I think if you put Hill (assuming he can still walk at his age) behind a good OL he will do pretty well... better than average (and better than Keenum). I also think he's one of the better QB's the Rams have had in the past 10 years but that's like saying "that's one of the better cheeseburgers McDonald's has made". Its not a strong sentiment.
That said, I completely agree with the uneasiness of Hill being your starter. I think he made some big time throws for the Rams but the OL was historically terrible, otherwise I don't think he would be the whipping boy for Ramerica. I hope Goff is the answer at some point... but idk.