I love the size of a 40B in general, but especially for starting the hobby. It's so much less overwhelming and quite frankly, less expensive. Even with years/decades of experience under my belt I still don't like large reef tanks, I like looking at them, but not owning them. I feel like a bad American saying bigger isn't better, but I considered it an upgrade when I downsized my last reef to smaller tanks. 40B are inexpensive on sale and used, work on making that really nice, quality over quantity, and then if you decide you want a larger tank it's a good sump or QT system! But focus on making a smaller tank fantastic is my suggestion, there are plenty out there to show it's very easily achievable.