I just did a clients garage floor in tiles he got fromm Costco for 2.00 a foot(slate grey diamond plate pattern) .I charged him 350.00(app. 450 sq. ft.) for labor which included painting some of the exposed foundation concrete black to blend with the floor.Installation was fairly easy. I used a table saw to cut the tiles where necessary.They are more comfortable to walk on than the concrete. Tiles are going to cost a lot more than painting. So I think the cost differential between the 2 methods is a big factor. As for which would last longer from a wear standpoint...i think the tiles would as long as they don't break, but this is pure speculation as this is the first experience i have had with tiles. I have painted a garage floor in epoxy before and it will wear and need repainting. Tiles look better.Very uniform look and the diamond pattern looks good.
P.s.: Why finish the floor first? That should be the last thing you do