Ha, didn't see this thread before, else I would have chimed in
My vote: If it is a sunny day, Redwall. If not, upper Fall. Or Rock Nettle?
I fell in love with Redwall when I first hiked it and I have never lost that love. On a sunny day, it is just amazing. I am a big fan of tall red canyons with red light reflected off one wall onto the other. Redwall rocks from as soon as you hit the canyon entrance. If you have only 4-5 hours you won't mind being stopped by the dryfall If there's a rope and you want to trust some random rope that has been in the weather for who knows how long, it's not really that scary looking to get up. The time I got past the dryfall I did the Talus Jack bypass. It was cool but took us a long time - admittedly not the fastest hikers. Redwall is getting popular. Last time there we saw another party, surprised the shit out of me, and there is some evidence of cars parking by the pavement. Helps to have a GPS or else take a careful compass sighting - the canyon turns to the right just after the entrance so you can't really see a big gash as you approach it across the fan Fan was not too bad.
Rock Nettle is awesome. But again, the reds are really best on a sunny day. There's more to explore - you really want to get to the upper canyon - and it's a longer slog. The big lower canyon is just another wash. Rock Nettle is a side canyon on your right but not a hard right, not long after a big reddish (IIRC) boulder in the main wash. We went up the slope in the middle (between Rock Nettle and the main canyon) and dropped down into the upper canyon, went up it a good ways in some wild red eroded slots in fanglomerate, then came down the bypass Steve shows in his site. It was just a bit tricky finding a little gravelly gorge to drop the last 20 feet into the canyon. A LOT of red there. Not the big high walls of Redwall, close narrow little passages.
Moonlight: long slog. Good stuff in there, but some work.
If you've not been above the big fall in Fall, it's good. Smooth narrow grey twisty. But you've already been to the lower canyon so.. But you know it is an easy approach. I've gone up the bypass (on your right on the way up) a few times and its not bad. No real exposure but a bit of air as you go along a smooth ledge to get behind the fall.
Palmer? I dunno, it was OK. The big red fall is pretty cool and massive. If you go from Titus there is a visible trail the whole way. Watch for the fainter left fork where the Fall trail turns up canyon. Try to eyeball a cairn or something on the other side of the Fall wash, or work around a bit once you cross to find the trail. There's several trails, I think sort of upper and lower. The lower trail crosses just below the HellHole (my name for it) and do catch the trail on the other side as it exits the wash. The upper trail works too, you just spend a bit of time following the HellHole down. For us, Palmer was a full day, starting at Titus parking, including a long lunch stop at the base of the big fall. We probably started around 9, as we'd slept at SPW and usually leave around 8.