It is true that you should start out with a bigger tank... let me explain
what if you were stuck in a house with some minor pollutants and the house is about 10ft x 10ft, now, imagine yourself being in a 50x50 (50 gallon, i know thats small for a house though. haha) it would be alot more comfortable because you have more moving room for yourself and dont get cancer and all that yuck.
Water parameters and such act the same way in bigger tanks. If something dies off, the water wont be affected as adversely like it would in a 10 gallon. A 10 gallon can only also support about 3 -4 inches of fish ( a guideline, not limit) and a bigger tank would open you up to a new world of tangs and the bigger boys. (maybe not grouper

)
But... It depends on your budget. You may dish out about the same cash for both ( Which alot of people say) but this is my opinion:
Wouldnt it cost more for about 60 lbs of live sand(about 60$) and another 100 lbs of live rock(live fiji rock at my LFS, local fish store, is about 4.99 per lb fully cured) than it would in a 10 gallon?
but for those non-determined, maintainence in a 10 gal will be alot more laboring than a bigger tank.. why?
evaporation is one of the many reasons.. a 10 gal evaporates veryvery much quicker than a bigger tank and you will have to top it off with some RO water (salt doesnt evaporate with freshwater) and you will have to get it between 1.21 - 1.23 SG (specific gravity, which can be measured with a hydrometer) for fish and about 2.21 - 1.24 for inverts.
MY opinion is.. If you're fairly new, start out with bigger because it is, in the fish world, better to go bigger. (if that makes sense)
And be ready to spend at least 80 (which isnt bad) to get a 10 gal, a filter, maybe a skimmer, some saltwater (of course) lights and fish, inverts and live rock.
Alot of this stuff will e covered soon.. Im thinking of writing up a topic on it..
I learned all of this stuff in about a month or two and even a 15 year old can learn about it. you need to look around and do research!
whew, long post