I maintained mid-status on both CO and AA (Gold and Platinum, respectively.) I eventually moved all my business to AA because of AA upgrade policies, status treatment and good award availability. That resulted in reaching top status,a nd it has been more than worth the change.
As Platinum on AA, I can purchase 500-mile "stickers" - these are electronic domestic upgrades, each usable to upgrade up to 550 miles US / North America, Mexico, Central America and Caribbean on almost all fares, including deep discount economy. They cost $30 each, and I get four free every 10,000 flown miles, basically. My upgrade record as a Platinum was not bad at all.
I can also purchase upgrades to long distance international destinations with miles and $250 co-pay that will include up to three flights in one direction. Again, my success rate was pretty good, depending on day and time of day, season, destination, etc.
As a Platinum, I could also access AA and oneworld lounges the day of international departure while flying AA and oneworld (those long distance ones again, and Mexico City) at no cost. You also receive, as on CO, preferred coach seating, access to the elite reservation line and First / Business check-in desk, pre-boarding and access to the elite security line.
I am forbidden to use the words "Coach" and "comfort" in the same sentence - whoops, I just did! But at least the ability to select exit row etc. makes it tolerable. I do not think one is better than the other, YMMV.
With all my business on AA, it has been easy to reach the highest status (Executive Platinum) and the benefits are much better - including eight annual "eVIP" coupons each good for upgrading up to three segments to the next class of service anywhere AA flies, and courtesy (free) "domestic" (see above) upgrades. I have never looked back with any longing.