You stay in Mestre because its cheaper than Venice. So you want easy access to Venice and the Tritone is ideal. Buses from the airports stop outside as do the buses too/from Venice, and you buy the tickets in a bar under the hotel (info in the folder in your room). Note they cram people on the buses at busy times with no maximum standing number. You are also opposite the railway station if arriving/leaving by rail.
Our room on the 5th floor was large, clean and the bed was comfortable. The buffet breakfast was good quality and regularly refreshed.
We were happy with our choice.