I decided that hyper-threading is better even if it were a bit slower because I want to keep one thread unused by Bitcoin and leaving a hyper-threaded half core unused by Bitcoin is better than leaving a whole core unused by Bitcoin. So scratch that request for a benchmark utility. There are other more important features to work on for now.
I think that a very useful thing to have in the BitCoin main window would be an indicator saying "# hashes/sec" to demonstrate how fast the BitcoinMiner threads were running.