There are some nice things about them, though. The reels may have aids to make loading the film easier. The reels may be adjustable, so that you can make one reel handle both 35mm and 120 film, and that old 127 that was in Uncle Oscar's baby Rolleiflex when he died. A good plastic tank and reels may be worthwhile if you can afford them. A good tank is going to be easy to assemble, because you're going to have to put it together in the dark.
Some tanks look like puzzles.
Beware of anything that requires parts to be seated in a proper position because it'll probably be a pain. Beware of anything that has more than a couple of parts to put in. Beware of anything that looks like it might break, go down the drain, or disappear easily. You may be surprised at the difference in fluid requirements for different tanks to process the same roll of film. A stainless steel tank typically requires 8 ounces for one 35mm roll of film, and 16 ounces for two 35mm rolls or one 120 roll.