Welcome to the forum, its a great place with great people.
Coming from someone who has purchased 4 tanks in the past 2 months.....take your time with the decision.
1st tank: 8 gallon nano. Small, cheap....that's about the only benefit. Water quality gets out of hand even after 1 overfeeding.
2nd tank; 29 gallon biocube. Pluses- all in one, kind of cool looking, lots of available mods. Biggest negative: I couldn't stand the fact that good retrofit or diy lighting for a reef was ridiculously expensive in my opinion. I'd much rather buy a light that can grow with me, be moved to another tank or scaled up by adding an additional unit. With lights typically costing more than the tank they're above, its a big consideration. I bought an AI Prime HD thinking I'd cut a hole in the top and make it look like a spaceship landed....nope.
3rd tank: 25 gallon rimless cube.
Pluses: I love the footprint, being 18 inches wide. rimless, more modern looking than the biocube. Cheap, and if you drill it, lots of possibilities.
Don't like the depth at 19+ inches. Don't like the fact that by the time you've spent the $$ on drilling, or overflow + the cost of a sump, you could buy a nicer tank without having to lift a finger. Don't like the fact that the sleek form factor is neutered by the need for an overflow (which spaces it away from the wall). Large HOB with media baskets= cheap but ugly solution.
4th tank: Cobalt C-vue 26 gallon AIO.
Pluses: All in one + the sleek form factor of the rimless tanks. Has an arguably better designed rear filtration compartment than the nuvo's. Comes with MJ pumps. (which is why I bought it). 24 inches wide, 2nd reason I bought it. At 24 inches, any clearanced out vanity, kitchen island, or small dresser can be used as a stand which allows for more of a furniture (or fun) look instead of the ubiquitous black plywood mafia that fish tanks are all members of. I would have preferred the 40, but at 36 inches it would have necessitated another light, which at this time would have increased the base project cost 50% and that wasn't happening, I guess I could have gone with 2 black boxes and it would have been cheaper than 1 hydra 26...but why get into the hobby and not get a beautiful spectrum that makes the coral look the best. It's like buying a corvette and running 87, so I'm sticking with the 26.
Will I regret it....probably. But I would arguably need a psychological evaluation if I again changed my mind and bought a 5th tank (Cobalt hasn't even arrived yet).
I can tell you this, I do agree with everyone who says buy the biggest you're comfortable with. If I could swallow the cost of a 2nd Hydra 26, I'd have had a C-vue 40 on its way right now....