I bought both.
RIG because it is way oversold, still under the shadow of the BP 2010 gulf oil spill. Also, Carl Icahn owns significant shares as an activist investor and has gotten them to agree to a significant divi increase. The floor on both stocks is determined by the divi, so a big divi increase will immediately result in increasing RIG's stock price.
SDRL because they are obviously committed to keep paying the 10% divi, also they are a good company with newer rigs.
RIG is a good value play. Although nothing too exciting, they sport a nice backlog, some newer rigs coming into play at some point, and Icahn forcing out some higher dividends. However, I've been skeptical of their mgt and they operate some antiques when compared to Seadrill. SDRL is a leveraged driller that will continue to pay a substantial amount of their cash flow in dividends and will likely "grow" into their dividend. They sport more effective management and newer equipment. They also seem to have strong relationships in areas which RIG doesn't such as Brazil. Seadrill also owns stakes in alot of other plays such as Sapurakencana, Archer, NADL.
So it depends on what you like...SDRL is viewed by some as more risky due to debt levels but given their structure, I dont consider it a concern but thats just me. They sport a high dividend and a large backlog among other things, that provide me comfort. Seadrill is at a better price now than RIG but RIG is less risky in some eyes. Also, Icahn will be pulling cash out of them until hes bored. I like ESV the most at this level but SDRL is a close 2nd. Long term, you won't go wrong with either ESV or SDRL. I own shares in SDRL.