I was going to add one last thing. If you really love a certain footprint, sometimes it's just best to go with the size that can be redundant. I stuck with the 30inx12in. A 29 and 20L are similar enough in volume and size to where you can basically just swap the tank out without new lighting, new filter, new co2 system, etc. Stands will obviously not need replacing. So when you just have to buy the tank, it's pretty cool when you want to switch up.
That's why I like the 60CMx30CM. My long term goal is to move my little nano to my wife's office, setup the 60P in the bedroom and set up a 90P in the living room. My nano is 45CM so I could go with more than a few options. I could swap out a 60P for a 60F and just keep one in the garage, depending on what I want. The 90P would never get changed out because that is my ideal size tank, can't go bigger than that and I think the size is perfect.
Just something to consider. If you got a 12 long, you would not likely find a way to use the equipment you buy for it on a different tank. Lighting would be swapped out, filter would be swapped out, etc.
Not to complicate the matter, I just think it could simplify the decision for you.
I would visit OVT's to check out not only the 12 long but also his other sizes. Unfortunately he doesn't have his 60P anymore (was my favorite tank of his). He has a good variety of sizes going, not exactly what you are looking for outside the 12 long but you can compare a shallow tank to a not so shallow tank with the same footprint, among others.
Again, if you want to swing buy and see my 60P, call or text me. Not just for the tank but I can show you ways to get a 60P or 60F setup more cheaply as I did a lot of research before I started it up.
Ok so this makes a lot of sense.
I like your master plan too! As those are the same tanks that I want as well. Though I wouldnt swap out tanks like you mentioned, but if I buy a light and I dont need it I can use it on the other tank to a certain extent.
I think this might have made it simpler for me to decide.
Although OVT has a point for the 12gal long yes it may work to a certain extent.
I've seen that 12gal dutch and its super nice and I love the look, I just dont think I'm ready for it yet. Lots of plants and planning locations. I'm going to wait till talon gets his going and learn from him.
Either way I will have to get in touch with you guys to see what you have. I'm scared though, I've always wanted that shallow cube that OVT has as well. It might complicate the decision :P
Now I just have to think which tank to buy first the 60P or 60F :P I'm leaning toward the 60F as I just set up the 29gal, so the 60P might be similar.
Thanks for all the help! I may do my first journal when I get all the stuff together, but it might not be until christmas time.