The switch is easy - click down and hold it down, but I would say if you are concerned about how easy the button is, a button is probably not for youl.
I've gone back and forth between the auto and the manual - here is my experience if it helps anyone:
I started with an auto - mostly because I thought it would seem natural. I loved it. Then I started to use a modified (cut in two) Greencig cart for direct dripping to slow my pace of using up cartos. That worked great so I thought I'd try direct dripping the 901 atomizer on my KR auto battery. I found that direct dripping a 901 atomizer on a KR battery is a total failure - too much free air flow to activate the auto battery properly and (unlike the modded Greencig cart) leekage onto and into the battery.
auto battery with Greencig = Success
auto battery with 901 = Fail
Well, I had heard rumors of auto battery's self-activating in your pocket and I wanted to use my 901 atty's so I bought a manual battery. The 901 atty had bad air flow, but after improving the air flow by replacing the whistle tip with a KR carto condom the 901 atty worked great on the manual battery. The manuals are sealed so you don't have to worry about leaking into the battery and you also get better control over the air flow of the 901 so you can manage the atty to prevent it from leaking out the side.
Anyway, I decided to try the modded Greencig carto with the manual and...it didn't work at all with the manual battery - no air flow at all due to the difference in the connection tip of the manual battery (auto has an air flow notch).
manual bettery with Greencig = Fail
manual battery with 901 = Success