Since they charge more for first it must be better. Well I suppose it depends what you're flying on. On a long haul flight with designated first, business, and economy sections, first is going to be above and beyond what you get in business -- sometimes with a great degree "more", sometimes with just slightly nicer and more spacious amenities. That doesn't mean business is bad, it's just not first.

However, often times on shorter flights or smaller planes there is less of distinction, assuming there even if a business class on the flight. Either way I'd rather be in First but if Business is what I book, I'm not likely to upgrade it myself.