I respectfully disagree. For example - lets say 'as a beginner' I want to buy a 50 gallon tank - well your advice would be buy bigger. Lets say 'as a beginner' I want to buy a 90 gallon tank - well - your advice - the way I understand would be to 'buy bigger'.TLDR, whatever size tank you think you want or have space for, double or triple it.
I'm still new to all this, but I'll still suggest that one of the biggest mistakes new reefers make is not buying a bigger tank. Anyone that does any research knows that a bigger tank is easier to maintain (though more expensive). However, what isn't as often mentioned is that you'll outgrow it before you even stock it.
I happened to have a 40 gallon breeder going into this so I just used it. I had it, I had a second one (spare, I guess, in case I broke this one drilling it) and I had a stand). That right there saved a good chunk of money. Plus, it had been up and running as a freshwater tank for the past 10 years, so it already had a spot in my house.
As of right now, there's no live stock in it and everyday I consider upgrading it to a 100ish gallon tank. As soon as I filled it with rocks, I saw how small it was going to be. Plus, and almost more importantly, the stand for a 40 gallon tank doesn't leave a whole lot of space for equipment. I have a 20 gallon long sump (which had to go in from above, so it can't be removed with the DT in place) and it leaves me just a few inches in front of it and on one side. I have a few things mounted to a side wall, but beyond that, there's not much space for anything more than wires and a few little odds and ends. For example, I've been hemming and hawing about an getting an Apex and one issue I have is that there's little to no room for it.
If this tank ever crashes, it'll be replaced with something considerably larger.I'm not sure where it'll go, but it's the plan.
IMHO - 'anyone that does any research' knows a bigger tank is easier to maintain - as you suggest - is not necessarily true. The research comes in - IMHO - when when decides to have a 20 gallon tank - to only buy fish that will fit in a 20 gallon tank. similarly - coral, etc. IMHO - maintenance increases exponentially with larger tanks. For example - there are threads here suggesting - just take out all your sand and rock - and rip clean it as a solution to algae - try that with a 200 gallon tank full of coral. Try catching a fish from a 10 gallon tank - as compared to a 200 gallon tank. Try scraping the glass on a 10 gallon tank vs a 200 gallon tank, etc etc etc. The costs (as you say) expontentially increase as well. Pumps, lights, salt, fish, coral, etc.
My suggestion - pick out 'how you want your tank to look'. Which corals, which fish, etc. THEN get some advice as to the proper size - then get that tank. If/when you want to upgrade - follow the same procedure. Far more people quit the hobby because of failure because they have bought a huge tank - and a huge bunch of rock - but then they cant afford the fish/coral etc needed to keep it up - they end up with boring rocks covered with small frags here and there - and a bunch of algae.
I will agree with you - stability - is easier to maintain - with a larger tank. If your heater fails - a 10 gallon tank will cool or heat up much more quickly than a 1000 gallon tank. etc.