Hi Kevin/Steve
Having a whole https sites tend to take longer to respond to the first byte and load i've found, which seem to be increasingly important in rankings.
I believe this can have an effect if the competition have faster more established sites and you are trying to get above them.
But another train of thought is that google may also trust you more if its a whole https site, so following Kevin's advice and having a https may be the most effective long term, unfortunately clients don't tend to like to wait.
Regards
Paul