I've done Taboose several times, and Sawmill once. Sawmill was only downhill, and I was glad it was in that direction. Prettier, but there was no water for a long way (mid September) between trailhead and the last place I could fill up. The trails can be done by horses so they are not very technical. Just hot HOT at the bottom. Shade is non-existent for most of the climbs.
Either pass, if headed up, I would start well before dawn, or late in the day after the sun goes behind the crest. Head up half way and finish the rest the next morning.
Sawmill is in pretty rough shape in some places, and on the west side you can easily lose the route in some of the more level segments.
Nothing really difficult about these passes. There will be less people on Sawmill, because it leads into a rather underused area on the other side. Taboose leads to popular Bench Lake and is a bit shorter and easier.
Interesting Trail - Taboose itself is rather boring. The area it leads to (Mather Pass, Upper Basin, Split Mtn, Cardinal Mtn. Vennacher Needle, etc) is one of my favorite parts of the Sierra. Sawmill, once you get out of the extended desert slog, is nicer, more variation and some nice lakes, but on the west side it leads to Woods Creek or Pinchot area, which can't match what Taboose offers in my view.
Sawmill has some really pretty spots on the east side, but also some burn zones
