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. This is important.
Many reels have gimmicks to simplify loading.
This is particularly useful if they have more than one kind of reel and you don't know which one works better. Agitation is where you stir up the chemical inside the tank and keep the chemical reactions going evenly and smoothly. There are, generally, three ways to do this. Cap the tank, pick it up, turn it upside down and then right-side up again to agitate it. Spinning by a spindle.