Unless we absolutely, desperately need the cash to get a really important deal done I think I'd fight to keep both, for at least another season.
When both are at the top of their games I think I'd prefer Emi because of his catching and his footwork, even if Leno might shade it as a shot-stopper. BUT... let's not forget Emi has only been in the side since Brighton, after the restart, so I'd hate to bin-off Leno and then find out that it was just a purple patch of form. I remember back in '98, Alex Manninger went on the most incredible run between the sticks to see us through the second half of the season, and we all thought he was going to be the long-term successor to Seaman. But then he just kind of fizzled out and never looked anything that special again.