A larger tank is more forgiving..and when I say larger tank I mean generally anything 55gal or over.
So when you are starting off learning about SWF and you didn't know for example (like me) that you shouldn't just pour a few gallons of water in all at once for evap, you have some le-way.
True it's a little more expensive upfront, but in a small tank if your not up on your evap, like you can't really miss a day. Your salinity will go up. Also depending on your stock, if you have sensitive stuff, they won't like that.
And when you're new...how do you know what's sensitive.
I'm like you I want to learn everything at once, but I've gotten ahead of myself and tired to hard and made a lot of expensive mistakes. And don't be fooled about the less maintence on a big tank. There are More things to do...just different sort of things. It lets you focus on other things instead of water quality.
On my 300 (which i'm still setting up), I have a 40gal wet/dry and a 65gal Fuge, I'm trying to raise the total amount of water..so Now I'll be around 400Gal and I'm sure my water will be rock solid for a long long time. Then I can worry about how to arrange the 500lbs of LR