it all depends on how much money you want to spend. if you dont have a lot but want a good chip, get the duron. i have a duron 800 and im working on OCing it. the athlon and the thunderbird are the same chip, i think. so basically all you are looking for there is the MHz to decide. the tbird has more L2 cache which helps in code compiling and stuff like that. but, IMHO, once you get to about 900MHz+...it makes no diff =) the tbird is rated to have a 8-10% increase is speed under strain than the duron. but thats fine with me...the rest of my system easily makes up for that. so its up to you buddy. thats just my .02 =)