E+ on UA is hardly worth it - seat pitch increases by only 4" with the same width. But, the price differential is not so much.

On BA, you get 7 inches of pitch, one inch of width, and two more inches of recline, but the price differential from economy minus can be pretty big.

Virgin PE has the same pitch as BA, but a much wider seat. IIRC, the price differential is the largest of the three referenced carriers.