This EZNEC plot shows the effects of dropping the ends of the 88' doublet. All three antennas have their apex at 40 feet. The black line is a 20m dipole in flattop configuration, the blue line is the 88' doublet in flattop configuration, and the green line is the same 88' doublet in inverted-V configuration with an included angle of 120 degrees (ends are 19.7 feet above the ground). The doublet is now slightly inferior (1 dB) to the dipole in flattop configuration. This isn't an apples-to-apples comparison of course: if we dropped the 20m dipole's ends down it would also degrade and the 88' doublet would again be the winner.