I recently evaluated this space for my startup's needs. We ended up going with Uservoice because it seemed to be more "product focused". As we grow we can opt-in to the different uservoice products that focus specifically on more product management (things like idea aggregation/voting, feedback forums, roadmapping)

Our support volume is manageable by just a few agents. If we needed to manage teams of agents and different support channels, freshdesk or zendesk might have won out as they seem to be stronger in that area.

That said, you can't beat a free tier if all you need is a basic ticketing system. Just thought I'd share some of the other options out there.