Lots of times you don't get to choose... they choose you and you go from there.
It's also more important to think of things from a happiness point of view vs a money and tin point of view... that's why I have stuck with a small 702/703 operator...
As much as people love the money that unions bring... I've never seen anyone who worked under a union truly happy. Just about every one of them is counting the days to retirement and complaining how the company is screwing them out of their time and a portion of their six figure salary and pension.
One thing about TS... look at how many tour operators have folded over the last few years.. and look at the seasonal and cyclical nature of the business and the rapid increase in the use of temporary foreign workers.