A genuine bench mark test would certainly be interesting! I haven't used Ubuntu/Xubuntu since I first started in Linux. I did find Xubuntu to be about as slow as Ubuntu. Now about LXde,...I've used it recently on just plain Debian Lenny,...and found it to be pretty swift! (I really didn't like the fact that I couldn't customize my desktop or icons the way I can in Xfce). And to top it all off,....I just use the standard Vector 6 on my older PIII computer,...and I find that it's just veeeeeery quick and responsive, using just Xfce.
Yes,...some really good un-biased bench mark tests would be good.