Unfortunately, my eye's don't let me paint anymore, unless its a door.but, I always found that 15mm (and, back in the day, I painted a LOT of 15mm figures) that its the best scale that you can add enough detail to make 'em look good, but you don't have to put in as much work as you do for something like 28mm figs. OK, I know that sounds obvious..........I also painted a mass of WH40K stuff, and whilst you can be a bit skimpy with the rank-and-file, you tend to put a lot of work into the 'personality' figures. I think that 15mm is a good balance scale-wise, and its easy to fit on reasonable size tables and generally looks good without too much hard work.
The last stuff I painted in 15mm was an ACW Union Division - 3 Brigades each of 4 regiments, plus some arty, a couple of cav regiments, supply wagons and a Reb brigade to supplement my buddies Confederate army. The figs were from a mixtures of manufactures to add plenty of variety, but a large proportion were by Old Glory, a company that are based not far from where I live.
“O Lord God, let me not be disgraced in my old days.”
'We few, we happy few, we band of brothers'