http://xorg.freedesktop.org/wiki/radeon
parece ter um resumo:
Radeon has some features not available in radeonhd and vice versa, but generally they are starting to be quite close while radeon supports all the cards and radeonhd only r5xx-r7xx.
Acredito que o driver radeon agora tenha o mesmo ou melhor suporte que o radeonhd . Os Seção" ATI Hardware "do" Guia de teoria prática da placa gráfica do openSUSE para usuários " parece concordar:
As of openSUSE-11.3 Milestone6 Novell/SuSE-GmbH have announced this driver superseded by the radeon driver, so it is possible the radeon driver may function better on RadeonHD hardware than the radeonhd.
Eu não sou um usuário do OpenSUSE, mas o driver radeon parece estar contido no pacote xorg-x11-driver-video , enquanto radeonhd é fornecido por xorg-x11-driver-video-radeonhd .