I like this tier-list of exchanges, it reminds me of the power supply tier list on tomshardware.com.
This list is a good start but I understand that it is based on personal experience, so obviously it's difficult to make it objective. So this list can be improved by community. My suggestion is to move Yobit to Tier 2, I've been using Yobit many times and never had a problem with them. Poloniex is in tier 1, I would agree with that few months ago, but not anymore. I had problems with withdrawals so Poloniex should be in Tier 2 at most.