the machined bevel gears are a good hop up, especially if u have a bigger/pokier engine in there - i had to do something as my os18 was eating the rear diff once a week or so... the steel ones i got have been fine since i fitted them. both gears in the rear of mine are the machined ones, and just the small one in the front is the machined one.

having said that... the 21 that auto2 put in his mt2 was fine with the standard diff - he maybe just got lucky. yea the machined gears look just like the standard ones, but they seem to work for me.

as for the one way diff - i have heard of one person who broke his within an hour while out bashing, and another guy swears by it, but he is a racer. personally, i aint tried it. it is supposed to stop one wheel turning opposite to the other, thereby giving better on throttle steering, but u will not have a front brake if u fit it... swings and roundabouts that one, i feel. bit expensive for what it is too, same with the gears, but if u have the cash, then go for it and let us know how u got on.

hope that helps.