I'm in the process of road bike shopping, and I'd like to know if there is a major difference between the 8-speed cassette and the 9-speed cassette? There seems to be a major price-jump to get those extra 3 "gears", and I'm wondering if it is worth it.

Problem is, I live in West Virginia (the state), so there are lots of hills and mountains to haul my butt up- no matter which road bike I decide on. I definitely need a triple ring set, but will 24 speeds be enough, or should I cough up the cash for 27?

Does it really help? Are those other three on the "extremes", or are they stuck somewhere in the middle of the range where I won't notice the difference?

So far, I'm considering either a Giant OCR3, a Trek 1000C, or a Specialized Sequoia, and all have the 8 speed cassette.

Thanks for any input!