I actually think all three are fantastic.
I'd say Betrayal is very intellectual. It's a classic text that's extremely subtle and nuanced. It demands the most rapt attention from its audience of the three, but the star power and great performances of the three leads helps with that.
The Sound Inside, I think, is the best play of the three. It's very tight, fascinating, and suspenseful start to finish.
Linda Vista is signature Letts' dialogue. I actually think Letts is indicting his protagonist throughout the script, but many audiences find him so repugnant, they can't stomach the 2.5 hour runtime with him at the center. I quite enjoyed it though. I do feel like the extremely graphic nude sex scenes are something to be aware of before you choose it though.