I ran both a big chief and lil chief for years. They are a good starter unit and you can do lots of things with them if you're careful. The little chief doesn't get nearly as hot and would be good mostly for fish/salmon, jerky, low temp kinds of things and that's mainly what it was designed for. The big chief has a larger element and can get warmer, and I've successfully done things like turkeys in mine, though it's not easy. I'd suggest building a tight fitting insulated box if you're going to get one. The thin aluminum really wicks the tempurature out of it if it's at all windy or cold.
That said, these days I probably wouldn't consider buying one new. If I found a good used one for cheap I'd probably pick it up, but for what a new one goes for it's not worth it. For a few dollars more you can get the MES. I bought one this past december and I find myself hard pressed to go back to the chiefs. The MES is very similar to the chiefs, but it works 100 times better and is a lot more versatile. The chiefs are basically plug in and go. It has no temperature control, no adjustable venting, etc. so you just get whatever temperature you get. The MES you can control the temp with the fancy little control box, so you can vary the temp from about 100 degrees up to 275 based on what you're doing.
Now, if you're hell-bent on getting a big chief here's a couple suggestions for you. I prefer the top-load over the front-load, as it just seems easier for me to deal with one big rack than four individual racks. Plus you can use the shell of the rack to hang turkeys or whatever from, haven't really found a way to do that with the front load. And it seems like the door on the front load never seals right. As I mentioned earlier, you should build a little insulated box for it to help keep the temps up. Mine was just a box built out of thin wood paneling with some fiberglass insulation sandwiched between two layers. There were a couple notches on the bottom and holes on the top for air flow. Did a good job of keeping the heat in. At the very minimum you'll need a wind break to surround the big chief, as even a slight breeze will suck the heat right through the aluminum skin. Make sure when you use it you plug it directly into the outlet, or use a very large gauge (small number) extension cord and keep it as short as possible. You want the heating element to get as much juice as it can, and a long, thin-wire extension cord will rob it of that.