My tile guy doesn't like doing the epoxy grout, he says it's much more difficult. For what it's worth he likes to do things the "old" way. He is good at what he does but doesn't like to experiment. I would have the same questions. Good luck! It will be beautiful.
Diane

I'd pay extra for using epoxy if it were meant to be white, but not black. The white epoxy stays that way for years and doesn't stain, which is great for counters, not as important for backsplash. It's really hard to work with epoxy, and it's not for the do it yourselfer. If you're going with black, I'd use the sanded and paint it. The grout paints are great and, you could always change your mind in the future and paint it another color and get a whole different look.

I dont know too much about the epoxy grout, but our mudroom accidentally had a lighter gray grout installed than what i requested. Our tile guy felt really bad and he purchased some grout stain. He used dark gray. It came out great, just what I wanted. We had used sanded grout. He said that he had used the stain before, but never on freshly done grout. He said it soaked in really well and took the stain really well. I would imagine getting a true black would be easy seeing how easy the very dark grey came out.

Hope that helps.

Thank you all for the feedback! After reading a bunch of reviews on the epoxies at the big box stores I've decided to go with sanded grout. It sounds far too difficult to use the epoxy and it may not even accomplish my goal. Since the sanded grout needs to be sealed I can use the grout paint as my sealant and get the color I'm after.

What size joint are you using? 1/8" or less could take unsanded. What grout? I'm surprised they would make a black that is actually light gray?? That could be an installer issue of using too much water. Call tech support.

Epoxy is tricky. Only use someone who is already experienced with it or you could have a real mess to contend with.

I prefer epoxy grout even though installation is a bit harder. Depending on type of tile you are grouting makes cleaning grout easier (i.e. polished marble is easy to clean). Hardest part is just keeping grout from falling down during installation.