I have only flown Virgin's E+ product. It really depends upon your own needs and the actual price. I was able to get a pretty good deal on E+ myself, since I was flying off season.

for me, the seat width is the biggest deal. In that respect it was incredibly more valuable. I would not have been able to stand that long a flight if I had a normal economy seat, and a full aircraft. Then again, if you are lucky enough to get an empty row, then you can always stretch out in Economy. United's E+ is legroom only, so I don't think it is worth too much.