I’ve had my Samsung Galaxy Tab (EU version with 3G) for just over a week now, great device. I’ve also used the Apple iPad (Wifi only version) for about 6 months and I wanted to do quick comparison between the two. Both devices are great, just different. Which one is more suitable for your needs depends on what you are looking for. Overall, I vote slightly in favor of the iPad for the moment because of its great battery life and sleekness of the UI but I still have hopes that the next couple of Android OS updates will even this out.
To keep things simple, I’ve listed the good and bad for respective tablet below. The good means that it clearly beats the competitor. I decided not to separately highlight stuff where they are evenly good (or bad).