Y! over cloudera
I'd pay for Y! support over cloudera. Cloudera charge 5K/server/year, in a big cluster its cheaper to hire some ex-yahoo employees (ebay did this).
Y! have dealt with the problems of large clusters, while Cloudera have focused on small deployments, and don't have the ability to test at scale, let alone focus on those problems.
together, both areas need work on, but Y! are more like RedHat -the big contributors of code- while Cloudera are like Suse