The width of the blade.....You don't want anything too big to start out with. Once you get the hang of things you can go to a wider blade if you like. It's all about preferences, some like BIG blades some don't.
Now in my humble opinion I disagree I found a 7/8 or bigger to be easier to handle. I have blades from 3/8 to 15/16th and they are all good. It is just a matter of preferrence as you said. For me bring on the big guys.... lol