That's the question you ask yourself if both are on your bench, though.
It's not the question you ask yourself if one is on your bench, and the other is not on your team.
Thomas, for what it's worth, has a batting line of 313/.353/.875 as a pinch-hitter with the Cardinals. He's one-for-two in that role this season.
Pujols would be a must-see at-bat for sure. No debate there. But there's no real evidence as of late that suggests he would be a more competitive at-bat.
If the Cardinals are going to turn away from the mission statement of figuring out their outfielders for a reunion, I can see the argument for it. They'll just need to own it. They pivoted for nostalgia, hope and the marketing opportunities that came with it.
Because those are the only things guaranteed with a Pujols reunion.
Again, that's if he's even interested in that assignment. He is no longer with the Angels because he was not interested in it there.