2 aspects to this post:
1) Humour:
I...........have a cheap BJ
:lol: ROTFLMAO
2) Helpful comment: I too bought the ferm jointer (I refuse to use the phrase BJ in my comments....) because it was so cheap that I figured it was a pain free test case... I also bought the axminster pocket hole jig for a subsequent project.
If I were in your shoes, now I have played with both, I'd buy the biscuit jointer. Why?
Firstly, as you've noted, it leaves, if properly planned, 'invisible' joints. Pocket holes can be arranged to be hidden, but unless you plan to apply a sheet over them, will be visible somewhere.
Secondly, the comments about cheapo jointers' cheap fences are correct, but, IMHO, irrelevant for a hobby woodworker. If I had a production run, it would bug the **** out of me, but for the sort of volumes I do, I will set up the cut with test pieces first, and monitor each cut: the Ferm's fence has not been a limiting factor for me.
Thirdly, pocket hole jigs at this sort of price range seem to have 2 intrinsic problems: Firstly, there is 'creep' as you drive the screw. By this I mean that as a result of the angle at which you drive, there is an almost unavoidable tendency for the 2 workpieces to move slightly out of initial alignment as you drive the screw. I don't know if this occurs with the better jigs, but it has been a factor in all my playing with the axminster set up. Secondly, and something that I was not expecting at all, the jig is essentially aimed at stock that is 3/4" thick or greater - any less, and the geometry means that your screw breaks out the far side of the stock before it reaches the other piece it's 'aimed' at. I keep thinking there must be a simple 'spacer' type arrangement that will solve this, but I've not yet thought out one that'll work.
In summary, I quite deliberately used both methods when knocking together a set of workshop cabinets out of MDF, ply and chipboard, in order to assess them. If the piece I was making required absolute confidence in alignment, the ability to work with stuff less than 3/4" thick, and/or hidden fixings from both sides, then there's no question which I'd use. The only downside to the biscuits is that it is, realistically, a little slower, and you do need to make test cuts on identical thickness scrap to work out your shim/spacing issues. That said, I'm pleased that I've now got both tools in the shop. Neither is really about high end cabinetry, but both are an aid for 'quick and dirty' stuff, like shop cabinets, MDF kids' beds, etc, etc. HTH...