Both OXY and COP are well respected oil companies whose business models are similar. But there is absolutely no doubt that, over the last 12 months, COP has easily outperformed OXY. COP's pps has risen 20% while OXY's has fallen 5% over that same time period. Furthermore, COP pays a 4% divvy while OXY only pays a 3% divvy.
The only thing that I have to say in OXY's favor is that they are currently looking to take the same steps that COP did, 18 months ago, and break up their organization to increase shareholder value.