When looking for solutions for our business, I personally looked at Aautotask. I am not the decision maker so I don't know what my boss looked at in full. Autotask seems good. It looked like it got a bit complicated and may be for very large enterprise customers. Just lots of features that we don't need.
As a single freelance consultant Sherpadesk has exceptional ROI because it's free but if my company had more support people I would definetly go with SherpaDesk again.