ZAFDeltaForce said:
Get any wired Logitech/Razer/Saitek/etc mouse that feels comfortable to you. Generally, mice fail in about 3 years regardless of price and quality (Not all mice, but it happens eventually)
As long as it feels comfortable in your palm, get it
Aside from the £5 mice I get from the computer fair (the type that only come with two buttons and a wheel, and a life expectancy to match the price), the only mouse that has ever failed on me is a wireless Logitech trapball mouse. And that only failed because my brother pulled the wire out of the receiver. My X8 and my brother's two Saitek Cyborg mice have worked just fine since day one, and show no sign of breaking down. Generally well built mice will last for life (so long as you treat them as mice).
As for how comfortable it feels in your palm... you can usually get a good idea just by looking at the pictures and the shape of your hand.
Btw, it's the SideWinder X8 that has removable weights. I don't think the X5 does, because that's basically a cut down X8.