Mountain Bike help.

[MelvinsArmy]

I don't know that you're going to notice a huge difference between 21 and 24 speeds. I can't even tell you how many speeds either of my mtb's have without looking at them and counting the cogs. One is a 94 Gary Fisher Aquila that is stock, the other is a Soma Groove that I built up from parts. I know that they have a different feel in various gear changes, but they both do pretty much the same thing. You're definitely going to want to make sure you choose a bike with a front derailer as well with all of those hills.

[RER40]

I don't know that you're going to notice a huge difference between 21 and 24 speeds. I can't even tell you how many speeds either of my mtb's have without looking at them and counting the cogs. One is a 94 Gary Fisher Aquila that is stock, the other is a Soma Groove that I built up from parts. I know that they have a different feel in various gear changes, but they both do pretty much the same thing. You're definitely going to want to make sure you choose a bike with a front derailer as well with all of those hills.

Gotta agree with this too.
Much like the whole discbrake coolness thing, gears seems to be the other the average person way over does. Who outthere really uses all 24 or 21 gears? Sometimes I almost wish for some simple 3-speed setup. Unless you're really doing competitive riding, all the doodads and whatnots are of little use. When ultimately to me comfort, the bike fitting YOU and being comfortable to ride for an extended period, is the biggest parameter that should be taken into consideration.

[aconsola]

frame fit is the most important thing to start with. everything else can be easily changed.
I use probably 12 of the 27 possible combinations on my mtb. There are less than 27 realistic gears that can be used as you want to avoid too much chain angle. The thing that the higher gear counts give in my experience is that they usually have a couple bigger cogs in the rear that are very useful for some of the steeper hills and more technical sections. I almost never use the big ring up front for actually driving the rear wheel, it is usually used for cranking over logs and protecting the gears I do use from rocks.
so don't look at just the number of gears, look at the ratios. 8(or9)x3sprockets is nice, but if it is only a low gear of say 22f x 28rear you would be better with an 7 speeder that has 32rearx22 front for the lowest ratio.