I wouldn't knock the Genie 3 too hard - certainly, there's a lot of people talking up its abilities, I'd suggest an order of preference might be, of those you mention, the P3, the _2, then the Genie 3 and the P1 at the foot of the ladder.
Why?
Not sure the P1 is there for any great reason tbh - spend a little more (I think about £50 or so) and you get the P2. I think Rega wanted to dip a toe in the budget sector on its first rung but not so sure it's a raging success. Hence the Genie would be my third out of the four.
The other two, well, no surprises there. You need to spend some serious cash to outperform those two.