I'm sorry, I find the weight argument to be absolutely ridiculous. Are we all losing muscle mass at a rate that holding/hauling 1.5lbs of tablet is a problem? How did our grandparents manage it when they had to carry around 15lbs typewriters.
On topic, the Xoom looks and feels better built than the Galaxy. More metal, less plastic = quality feel.
The Xoom weights 1.6lbs and the Galaxy weights 1.32lbs so if 0.28lbs is enough to hold you back, the Galaxy is the tablet for you (it is also slightly thinner).
On the screen, I have not noticed any difference, but some people swear the Galaxy has a crispier image than the Xoom. The Xoom's screen is supposedly made of an extra-tough glass - some say that's why it's difficult to find screen protectors, because Motorola thinks you won't need one.
If a tablet camera is important for you, the Xoom has a 5MP back camera while the Galaxy has a 3MP camera, but both take pictures of mediocre quality when compared even to an old 5MP camera (and you will look silly lifting up your tablet to take a photo of the Statue of Liberty or something).
Both have the same processors; memory depends on how much money you spend; GPS, Wi-Fi, BlueTooth, etc...
The Galaxy suffers from a deplorable lack of ports, but with that said, half the Xoom's ports are still pending software updates from Motorola to work as they are supposed to, so even though you get MicroSD Card, MicroUSB and MicroHDMI with the Xoom, the MicroSD Card is non-functiona, it has been due for an update that will turn it on since March, the USB is good for nothing more than connecting the tablet to your computer to transfer files, or to your camera if it supports the proper protocol - oh and you need an adapter for that. Motorola says in the future we could maybe expect the USB to have Mass Storage capabilities (to plug in an external HD, for example), but there is no official word on it. So while the Xoom has a bunch of ports, they aren't what they seem. but eventually, the Xoom will have a MicroSD slot (up to 32GB) and maybe a proper USB port.
While the Galaxy doesn't have an USB port, an optional USB adapter / connection kit offers an adapter to allow USB thumb drives to plug in to the tablet.
I absolutely love the Xoom, but it is disappointing that the things that would make it stand out are still works-in-progress. It is a pretty close call, but I would recommend the Galaxy because at least you won't be angry at Motorola for selling you a very expensive "to be continued..." product.
If waiting is no problem for you, go for the Xoom!