Yes Delta wins on SWU's. However, if you fly domestic, which I do less these days, your chances of being upgraded as a Platinum Elite are very high. My experience is close to 100%. Companions can be upgraded for free as well.

Another CO perk if you fly on international J-class fares you get 50% bonus miles that count towards elite qualification in addition to the 125% bonus miles Platinum's get. Thus, on a 10,000 mile overseas trip you can earn 27,500 miles and 15,000 elite qualifying miles. On CO you can rack up awards very fast. Unfortunately, upgrade awards to Europe are very annoying to use and hard to get.

One further point to consider, CO and its partners often have J fares that are not competitive, so if you buy them I'd check the Delta fares against CO.