Not touching this game (yet at least), but to play devils advocate for you...Tyler Anderson has proven he can pitch very effectively at Coors. Hamels has not, other than one start there last year where he pitched 7 very solid. Might be as simple as that. I'm not sure how much weight you want to put into 7 inning from over 14 months ago.
Both teams hit lefties particularly well. But Coors is Coors. Most metrics indicate the Rangers have been particularly lucky this season. Only a +4 run differential but 18 games over .500. (Doesn't mean "luck" is regressing this game.)
Also, Rangers coming off a huge, grinding series where they take 2 of 3 from Astros including an emotional game in extras. Can they keep that going for an interleague series at Colorado?? (Personally, I don't put too much stock into that but may factor in.)