Just sharing my expiriance;
I've been running FHEMWEB over sll for a year now, and it was not very fast. Just recently I've upgraded my Raspberry Pi to a Raspberry pi 2. Thinking that would solve the problem.
And FHEMWEB was not really a lot faster. Due to a failing SD card, I've had to go back to my old raspberry pi.
A few days later I've got the idea of getting one of those SSL certificates for a cheap price, to get rid of annoying 'This certificate can't be check, this connection might be unsafe, are you sure you wanna continue' messages. I've paid 25 dollar for 3 years, which is reasonable.
And to my surprise, this made FHEMWEB go a LOT faster.
(again, not compaining or asking anything here, just sharing my knowledge...)