I was in the same dillema. I have tried both OSes on live CD - its so easy. I have never "realy" instaled SUSE, but I got a pretty good picture what Im using. SUSE showed lower RAM usage at startup (inspite all the claims that it is more bulky than Ubuntu), it felt a litle lighter, too. But just a litle. Menu is good looking and sharp, but it totaly complicates a real day usage of the system. Yast is the same thing - literaly as the control center in Ubuntu, there are some diferent apps, but they do the same thing in the same way, using same resources. Only "better" app was that novell firewall. But you have to sacrifice Synaptic pcger. If there werent for that stupid menu, maybe I would be using SUSE. And another thing, pretty big, I almost broke my neck installing the nVidia drivers, and the x server did not work! In ubuntu there are no hardware problems at all for my hardware combo.
If you like SUSEs "minty" look you can allways use Linux Mint 6 "Felicia" - the flavour of ubuntu that is suposed to imitate SUSE, but still stay Ubuntu (8.10) and keep the synaptic and get "Mint installer" and slick "Mint menu" suse style.
I have used mint, and its great, better than SUSE, really "minty" looking, but I came back to superUbuntu 8.10.