Tray.io is expensive and only makes sense in a few rare occasions where you need 2-way constant data binding in a 'loop' where Zapier is more like an automation swiss army knife. Tray.io is aimed exclusively at enterprise while Zapier supports businesses of any size. Tray.io is very expensive and Zapier is much more reasonable especially early on before you have massive amounts of zaps.
You may also want to look at Integromat but Zapier would be my choice in this case. I almost don't see Tray.io as being something worth considering for your particular use case unless there's a massive scale behind your product that I'm unaware of (absurd amounts of tasks in the hundreds of thousands).
Zapier also has a great community and an "experts" program in the event that you want to outsource your automation.