My vote is on the AMP. When I was researching annealers it wasn’t the cheapest but from a simplicity perspective I don’t think you can beat it. In the end I didn’t want to mess with an open flame design which narrowed it down for me.
How much brass will you anneal at one time? How attentive do you want to be to the process? I like being able to fill hopper and do something else while brass is annealed. If I wasn't doing very much I would just use a drill, a socket, and a torch.
If price is no issue the AMP is the go-to unit. If it is too pricey, I have been using propane for years with zero problems (aside from running out of gas when I am not diligent).