I have the Griffin 22 and 25. They are good solid tanks and easy to build on as they have velocity style posts. They can be a little finicky with wicking, but once you get it down I don't get any leaks or dry hits and good flavor. I don't have the Gemini so I can't comment on that.
I'll throw another couple for you to consider, the Boreas and the Avocado 24. The Boreas is a big tank with great flavor. It will leak if not wicked right or laid on it's side without closing the juice flow control. The Avocado 24 is my new favorite. Great flavor, easy to build and I have not had it leak. It is a Genesis style wicking system where the tank is below the coils. I wick it so the cotton is just through the wick holes not all the way down into the tank. You will have to tilt it to get juice on your wicks, but no big deal once you're used to it. Both the Boreas and Avocado have velocity style posts.
Watch some vids on any suggestions you get and buy what is right for you.
ETA: I'm not a big on tanks guy, so I have not tried a lot of them. Others may have better input. I prefer my bottom fed squonkers...