First welcome to the forum.
With regards to fermentors most are in reality the same thing a big bucket you can ferment in I like my stainless steel fermentor but a plastic one would do the same job at a fraction of the price. Of course their are pressure fermentors which I am yet to try so cannot comment on those.
If your just starting out with All Grain have you considered doing a small batch on the stove, the outlay is minimal and you can produce some pretty decent beer this way most recipes can be easily scaled down.
https://www.thehomebrewforum.co.uk/threads/have-a-go-at-simple-ag.51779/
This thread was what inspired me to give all grain a go, you may also want to consider BIAB brewing which makes it even easier. I don’t doubt that more complicated techniques or all in one machines produce excellent beer but when you get right down to it you can produce decent beer with nothing more than a big pot, a net bag, a heat source, a thermometer plus a bucket to ferment in (plus your grain, hops, yeast and a sanitiser).