Well I have experience with both H+ and H and I can say that with my operator H is much much faster and I usually get H+ outside of the city in villages etc...
I live in the capital city of my country so I am pretty sure they would use + in the city if it was faster instead of the countryside.
With H I usually get from 10 to 14mbps
With H+ 300-900 kbps max
But, of course I'm not an expert, so it may be just my ISP being crazy, or testing h+ on small scale, but why would it be slower ? questions questions questions !