if you're not o/c'ing, and its not going to be stuffed in a foot locker or something, then just get whatever is cheapest. the only exception i could think of is the 3 prong clip, if that is important to you. i wouldnt sweat it, personally.
btw, those durons are DIRT cheap! you cant really go ANY farther down than 30-35 bucks...i mean, look a pricewatch...pIII 500's are like 60 bucks (not correct, just an example), a new pII would cost more than a new duron with 3-4 times the clock speed and 4-5 times the performance!