I've had a mighty but overall preferred how much easier it was to clean and maintain the plenty. The plenty is probably 20% better at producing vapour over the mighty. Downside is you're hooked in to the wall socket as opposed to having a more mobile device.. but that's not really an issue for my use case.
As for bowl sizes you can pretty much make any size bowl you want. The most I've tried is 1g but it could definitely take more. I got a room full of clouds with that, was like the straw that kept giving. I usually use a liquid pad for that reason.