Mini-answer: Both
I have a veritable tonne of metal minis primed and still waiting to be painted, and a much smaller weight that have been finished off since I started back to minis again a year or two ago. It's easy to get interrupted, taking such time and concentration to get back at the hobby. I mean, it's so time consuming to do metal minis right. It is, however, ever-so-rewarding! But I'll often spend a whole week's worth of all my leisure time working to finish just 3 or 4 figures. (Sometimes more.)
The sculpts do tend to be so much nicer on the metals ... plus they're generally quite adjustable, so you can often make duplicate monsters look different by gently rearranging the arms, legs, tentacles & weaponry into different, dramatic positions.
Nevertheless, I can't negate the fact that D&D pre-painted minis are just so damn simple by comparison. You get sculpts for creatures and some PCs (halflings especially) that you'd never be able to find a proper equivalent for from Iron Wind or Reaper ... although sometimes it's surprising just what those companies do make. (Of course, the same is true-in-reverse if you want Monte Cook's Arcana Unearthed figures.) The D&D figures certainly started out to be crappy to the extreme, but they've made some big leaps in colour selection, paint application and even sculpture over the last several editions. So I've been picking up a lot of the really cheap ones, and the more expensive figures when I figure there's no other way to get an achaierai or a barghest, for examples. Also, I'm someone who likes the fact they've continued to make new orcs and kobolds and hobgoblins, because of course, one of the benefits of metal minis is they tend to come in packs of 4 or 5 kobolds in a set that are all posed and equipped differently -- and that just looks so much cooler in play.
In the end, I definitely prefer hand-painted minis, but I deal with plastic to fill in the gaps and make up for the ever-glaring paint-lag.