Before booking anyting I highly suggest looking at both UA and CO .coms and do so as 1 ways its $79 PHL-LAS with the tx = $100.40
I was able to find on CO a LAS-SFO-PHL which was $100.40 while it wasnt coming up on UA unless I did a Multi-city and then the exact flights was $400.40 on UA
So I purchased my PHL-IAD-LAS on UA and my return on CO.com
thusly will end up with apx 5800 eqms instead of 4800 and apx .0035 cpm instead of .0042 cpm
( I could have earned a few hundred more miles but it would have meant flying PHL-LAX-LAS and getting into LAS @ midnight, my way I get in @ 11am and have the whole day to try and decide what to do , not really much around Vegas now is there)