The fluval ceramic diffuser has worked well for me. It doesn't look as nice as a glass diffuser, but it is small, unobtrusive, and can be tucked out of the way.
I use 20 oz soda bottles for tanks around 5gal and 16oz or 12oz for tanks around a gallon.
Surface are effects off-gassing rate. It takes less than 10 minutes to rinse the bottle, add some warm water, sugar, and molasses (not totally necessary), shake it to dissolve everything, let the foam settle for a couple minutes, add yeast, and hook it back up.
I get two and a half to three weeks in the winter, about two, or just under, in the summer. If you do bi-weekly water changes, swap it then and call it good.
People over think it and over complicate it. Keep it quick and simple or go with a pressurized system.
I usually feel kind of guilty using the quick reply... my replies are rarely quick.