It really is going to come down to to each his/her own on whether a TeeBird and Saint can play together. However, I think in general you are going to find that most people discovered too much overlap to really carry both with a lot of success. More often than not they likely had second thoughts on those shots that fit into that overlap, ultimately destroying their confidence in either or both discs if the shot did not work out.
If thrown the same the Saint and TeeBird will seem like completely different discs. However, with just a minor change in hyzer angle and body position on the tee box you will find that the Saint and TeeBird have almost identical end result lines. Visually you will see that the TeeBird flies flatter whereas the Saint might have the slightest hyzerflip to fly flat at the end. But again, their results are so similar that you will see a lot of overlap. Maybe a light GL Saint combined with a heavy Champ Glow TeeBird might create enough separation.
At the end of the day I found that my Saints flew incredibly similar to my fairly fresh Pro TeeBirds. Since I am sitting on a stockpile of TeeBirds, it was more economical to move on without the Saints. However, and I can save any details for the Market Place, if I could unload about 14 TeeBirds I would have no problem reinvesting in the Saint and making that the mainstay.