I take back my doubts from my previous posts. After 36 hours of running Phoenix with several rigs and looking at charts on ethermine, I can say with great certainty that Phoenix is indeed better than Claymore:
1) With Phoenix, the Effective Hashrate zig zags across the Reported Hashrate very closely (which by the way, is already slightly higher than Claymore's Reported Hashrate).
2) With Claymore, the Effective Hashrate line would be underneath the Reported Hashrate more often than not. It also fluctuates a lot.
3) With some cards, Phoenix run about 1 degree Celsius cooler.
4) The lower dev fee is very welcoming
I'm a developer myself, and I can understand/appreciate why the Phoenix Miner is better from an engineering perspective. Simply put, the Claymore Miner has grown to become a big messy code base with many features. It supports many alt coins not just for one, but two platforms (Windows + Linux). With Phoenix, the developers can dedicate their time on optimizing Ethereum mining. No gimmicks. I truly hope that Phoenix will continue to improve on the speed optimizations, and not worry about dual mining, Linux, etc.
Keep up the great work Phoenix Developers.