I would say that snorted meth lasts closer to 6 hours in duration...
As for the effects of crystal, well, they vary depending on how you choose to do it...
Smoked -- Lots of rushes, euphoria, gets you quite fucked up, very speedy, shitty comedown
Snorted -- Not nearly as much body high as with other routes of administration, very jittery, speedy, good head high, fairly shitty comedown
Orally -- Most euphoric way, VERY rushy, great body high, lasts a long time (6-8 hrs), very smooth (not jittery),and a more gentle comedown
IV -- Intense body high, short duration (~4 hrs), nice euphoria, not too jittery, tolerable comedown