I would also go with the 6.49.
It doesn't have the WinMe shutdown problems like the 6.18. And it doesn't have the problem of waking up the monitor after it shuts off (you know, the setting on the screen saver tab) like the 6.47.
There is maybe no performance increase over some of the other versions, but it certainly isn't less and there are a lot of things fixed in the 6.49 version.