I'm an old winemaker, so star-san and Iodophor are new(ish) to me. I always potassium metabisulfite for sanitizing, until I started making beer.
It works for sanitizing equipment. BUT- it takes a longer contact time, a pretty heavy concentration of sulfite (and it stinks and is irritating to the skin and lungs). I never use sulfite any more for sanitizing, not even sanitizing my wine equipment- I use star-san almost always but sometimes will use Iodophor.
There are a couple of advantages to these other sanitizers- one is the color and/or foam. You don't have to wonder if you've hit every spot- they coat the surface so that you can see what you've done. Star-san can be kept for months once mixed, so a gallon of mixed up star-san can last a long time.
One Step works, too. I used that in the past as well, and never had an infection. Any of these sanitizers are really personal preference. I like the handy markings to measure the star-san, and I like that it doesn't have any staining or odor. Others like some of the other sanitizers. Pick one, and see how you like the ease and convenience.