Hi: This is Anna with the Do Good Toolbar team. Long time reader, first time guest poster.
In terms of our favorite PPC engine, we would have to pick Google Adwords. There are several reasons why we prefer Adwords:
1. Quality of traffic. Google traffic converts better for us than any other PPC engine.
2. Metrics. We operate on a very tight margin, currently, we make about 66 cents in revenue for each download of the Do Good Toolbar. Of that, half goes to charity. So, knowing, *easily* which keywords are performing well is a tremndous help to us.
3. Tools. MSN Adcenter and YSM lag far behind when it comes to easy to use tools tp help manage keywords.
4. Interface. Adwords offers a much easier to use interface compared their big two competitors. Response time on the other networds is often painfully slow if not working from a T-1 or better connection.
5. Cost. As mentioned before, we have tight margins. If we had to pay the 10 cent minimum on Yahoo, then our already negative profit margin would go into the triple digits. Adwords is so much more inexpensive in this regard.