Sheila the difference between those two bikes is more than that one chain ring. Read Sheldon Brown for lots of information about bikes (he's on the web, google him)

There are probably better brakes, better components, lots of things better on the more expensive bike. So they don't break down as much, they run and shift more smoothly, and they weigh less.
I know one thing, the less expensive bike has the same geometry. So if you're feeling tentative, and don't want to spend $$ but you want a bike that fits you, try that bike.
Most of us end up getting a better bike, so good advice is to get the most expensive bike you can possibly afford.