The most imporatnt thing to chose a bicycle is frame, its the heart & soul of a bicycle.
You can upgrade your components but cant upgrade ur frame. so always chose a right frame size according to your height.
Second thing is fork ( Shock Absorber) & third is wheel quality.
If you want to use rough then you should chose a bike which has front shock absorber. no need for rear shocks.
Nowdays alloy frame is very popular which is very good light in weight & rust free , low maintenance .
Frame vary according to your height & wheel size is always standard (MTB 26 wheel size)
Funda is very similar to your cloths . A fatty man wears a small size of shirt then its a problem or vise versa.
tell me your weight & height so that i can suggest you a rigght bike with right frame size.
Can Call me 09811981365
You can visit at www.firefoxbikes.com (Amazing bikes)