I know nothing about the First Gear heated stuff. I have owned multiple heated jackets and vests, though. Here is my experience in order of what I owned and when:
Gerbing: In 2000, I acquired a Gerbing jacket at the moto show. At the time, Gerbing was selling trollers from Warmnsafe, and that is what I got with the jacket. It was great and I wore that stuff for years, but eventually developed some complaints. 1. The neck fire thing, same as T.J., and handled similarly - I needed more than just a turtleneck, but a bandanna around my neck over the turtleneck was adequate. 2. The power cord came out inside the jacket, which meant that when I tucked the jacket in I had to somehow route it under the hem of the jacket then back up and out over the waistband of my pants. 3. The fit of the jacket, which they call unisex but really, it is men's. It had a straight torso with elastic around the bottom hem. Fully half the heat in the torso, was below my waist, and the cut of the jacket meant it was a real production to get it tucked in under my riding pants and smoothed down so that I didn't end up with half the heating element bunched in a roll at my waist. Once I got it stuffed in there correctly, snaking the power cord down and under and then up and out, was always hard. And I needed a middle layer that was fitted, to snug it up to my body, because it fit like a sack. On the bright side, it is nice and warm to have heat all the way down to where your butt touches the seat. But the constant pulling and tugging and bunching, eventually caused the jacket to develop a break in the wire and quit working. That was after about ten years of heavy use, though, so I really can't complain. I did not buy a new Gerbing jacket because the new ones are thicker, with some insulation over the heating elements, which would make it even harder to juggle the lower half of the jacket. I took the jacket apart to see what was inside and it really does have tangled up wires that are not very firmly anchored.
Gerbing has also, since I got my jacket back in 2000, started making their own trollers rather than sourcing the warmnsafe ones. I have not tried the new trollers, being 100% satisfied with the warmnsafe trollers, and the price being the same.
Widder: In 2001 or 2002, I acquired a Widder vest, used, as part of a package deal with some Widder gloves I wanted. The vest was nowhere near as good as the Gerbing jacket I already owned, so I gave it away. Widder is now gone, so they're not really a choice any more anyway. But there are a lot of used vests out there, they were once super common, so maybe someone here has one or will get one as a castoff. They're out there.
Gr8Design: This was the new technology at the time, using carbon fiber fabric for the heating elements. The vest works great, though it's a vest, not a jacket, and it's kinda stiff. The heating elements distribute the heat much better. But, it's not available any more, and they're not common on the used market, so praising it doesn't much matter.
Warmnsafe. I bought a Warmnsafe jacket because they had one in a women's cut and I like their trollers so I was inclined to give them a shot. It fit a LOT better than the Gerbing and used less power. And the power cord exits the jacket on the outside! Hallelujah! It would have been every bit as warm, too, except that it was shorter, which saved me a lot of tucking-in-hem-juggling, which was great, but didn't warm my butt like the Gerbing did because it didn't extend that far down. I still would have preferred it except for one thing: It had thick wires that ran across my shoulder blades, under my leather jacket's armor, which irritated me. A lot. So I could only wear it when I was wearing one of my softer jackets that didn't have armor plates that closely hug my shoulders. I eventually gave it away to someone shorter who wore a softer riding jacket. I wouldn't rule out buying another of their jackets, though - they have gone through two or three iterations since the jacket I bought, and they may well have fixed this issue with the shoulder wires. I do think they showed the most thoughtfulness in their design, of any of the jackets I have owned, which bodes well for them resolving issues like this shoulder wire thing.
Powerlet: This is what I am currently wearing. It is a men's cut, once again, so it has some of the tucking-in-hem-juggling issues, especially since they also followed Gerbing's lead, putting the power cord on the inside front of the jacket. (Since I know the guys at Powerlet, I have told them repeatedly and strenuously how much I hate having the cord on the inside.
They didn't understand it until I showed them how I was tucking their jacket into my pants. Men's pants, the waists are lower, so guys don't have to do this.) However the Powerlet jacket does NOT have elastic at the hem, and is not quite so long, so the tucking-in is not as difficult. The shape of the jacket is better; it fits properly closely without needing something fitted to go over the top and snug it up to my body. (Though a snugging-up layer still improves it.) The heating elements are softer, I don't get a sense of tangled up wires at my waist. And the neck is the right amount heated, I don't have to shield myself from it.
So as you can see, I have not found the perfect heated jacket yet. But even the worst ones are vastly better than doing without. My advice is to examine some heated vests and jackets, try 'em on if you can, and get what works for you.