I prefer incubators, because I am too curious for my own good and find learning about incubation to be one of the most fun parts of poultry raising. Is it easier? Not even close. Broodies are dead easy if you've found a reliable one. Just stick some eggs under her and pull out the products of a 90% hatch rate 21 days later. If you have a good incubator and a turner it isn't too much harder, but there's still some temperature monitoring involved that isn't there with a broody. Like noted in the original post, you have to have a plan for power outages or risk losing much of your batch. For those of us on solar electricity, the standard light-running configuration of DIY incubators is a power drain and would be best at least swapped for a more energy efficient incubator if not a broody. I am still 'plugged into the grid' so I can persist in my incubation without too much worry except for that of having to pay a little for whatever energy I used and didn't produce. Also, you then have to heat the chicks you hatch, which gets pricey fast if you're not using a heating pad.
The downsides to a broody, and in reverse the upsides to an incubator—in my opinion—are inability to mark chicks at hatch as being from a particular sire or dam; it's hard to use hatching baskets under a broody. Sure, you can set eggs from two birds only, but that gets old pretty fast when you want to hatch large quantities including different pairings at the same time. If you're trying out a broody to see if she's a good one, I suggest having an incubator warmed and ready for maybe the first week and then keep checking on her when they're hatching. I have yet to have a bad broody hen but they do come around now and then. Broodies also don't lay eggs, meaning you have two or three months of zero eggs from that hen. That's $28 in possible egg sales money (if you sell at $4 a dozen) that's gone. You can run an incubator for less than that.
Broodies have the advantage of the bird being on home soil from day one. They're wiser, tougher, and seem to be raised to be smart about predators. They learn robust foraging behaviour from momma, and c'mon, if you don't think a hen leading her babies around is cute you must have a heart of stone. I let a broody raise a few batches per year and I think it's the best start they can get.
As to mortality rates; at this point it's not a fair comparison because I have hatched ~70 in an incubator and maybe 15 or 20 under broodies, but it stands to mention I have lost 3 chicks from manual incubation and brooding (intestinal prolapse, mushy chick, and a brooder accident) and only one under the hens, which was entirely my fault. I left a water bowl in reach that was too deep and the chick drowned.
But it can be challenging if the hen isn't separated from the rest of the flock, in fact that can be harder than hatching with an incubator.
