Uhm, I don't think so? Before Gmail was fetching all the time which meant the process was active at all times, now it's terminated so I would assume battery life will improve.
The process just listens, it doesn't actively seek out anything. The process is still "active" even if you manually sync. With a
scheduled refresh you will be "hand shaking" every time so this obviously uses more power than push. If you're only manually syncing 5 times a day, this can't be on that level so you may see a small increase (well you probably wont "see" or "notice" the difference) in battery life.
You'd have to have the screen on to read them anyway but it would be on longer with a manual sync as with push the e-mails would be already there and pull - you'd have the screen on whilst waiting for them to come in.
I don't think you will see any noticeable difference, but will be interesting to see your results...