As a rule for all concerts, I prefer lower level, as close to the stage as possible. Unless you're in the first 10 or so rows, your view can be seriously, maybe completely, blocked on the floor.
We saw TSO last year on the lower level directly next to the stage (handshaking distance - it was cool.) Although we were very close, the lighting effects may have been better from a more straight angle. It was a sit down crowd, so maybe the first section or 2 of the floor wouldn't be bad. I'd say ideal for TSO would be first level, first few rows (maybe first 10), maybe almost to the center of the arena. That would give you the straightest, most unobstructed view.
Have fun! I'm going to pass this year because I have 2 concerts in the next few weeks. But they were so worth it. It's a really, really long show, be prepared.