Overseer Fight: Allos or Therizinos?

I'm getting ready to attempt Alpha ascension on single player and am wondering what dinos to bring. I'm planning on a couple Rexes to clear the Tek Cave, a Yuty or two for courage, and then either Therizinos or Allos for the Overseer battle. The Therizinos are already bred with a bunch of health and damage mutations, but I only have primitive saddles. The Allo stock I have is just decent wild stats with no mutations, but I have a 141.9 armor saddle BP.

The Therizinos would be much better given their mutations and the veggie cakes I can give them, but I'm not interested in the crap shoot that is the swamp cave, especially considering how rare Therizino saddle BPs seem to be. The Allos would have much worse stats, but I would need to grind 6k fiber, 10k hide, and 1k metal ingots per saddle. That's not a fun grind, but it's a known commodity versus the lottery of swamp cave red drops. I could breed them up a bit (or a lot if necessary) while grinding the saddle mats.

Which method would you recommend? I also have a Rex army and 116.5 saddle BP that I used to take out the dragon, but trying to get them into the cave in the five minutes and then down to the portal doesn't sound fun by myself, not to mention that I think they'd be too slow to keep up with the Overseer.