I first tweeted about Ubutu 9.04 a week ago. Now I know I’m not exactly comparing apples with apples, since MEPIS 8 is based on Debian 5.0 and uses KDE 3.5, whilst Ubuntu 9.04 uses GNOME 2. More here
The overall score is MEPIS 3, Ubuntu 1.5. This scoreline is obviously subjective, but you’ve heard all the good things about Ubuntu, have a slow(er) laptop, please do consider MEPIS. Both MEPIS and Ubuntu support audio/wireless networking flawlessly, unlike (cough, cough) Debian.