"the 12 bar is more simple, with fewer chord changes, so that there are fewer beginnings and endings to worry about, giving you a lot more freedom" Forty-eight bars of ordinary 12-bar looks like this: I-I-I-I-IV-IV-I-I-V-V-I-I-I-I-I-I-IV-IV-I-I-V-V-I-I-I-I-I-I-IV-IV-I-I-V-V-I-I-I-I-I-I-IV-IV-I-I-V-V-I-I. Forty-eight bars of ordinary 16-bar looks like this: I-I-I-I-IV-IV-I-I-IV-IV-I-I-V-V-I-I-I-I-I-I-IV-IV-I-I-IV-IV-I-I-V-V-I-I-I-I-I-I-IV-IV-I-I-IV-IV-I-I-V-V-I-I. The first changes chords 16 times, the second 18 times; not much difference.

"one of the cool things about 12-bar blues is that you can work out a short lead phrase and repeat it over all the changes to good effect--not so much with 16-bar blues." A phrase can be repeated over all the changes the same way in 16-bar blues as in 12-bar blues. The only section the 16-bar blues adds is another IV-IV-I-I, which is in the 12-bar blues already.