I posted about the Medion in the Forum last week and its very good value.
About the Dell. It needs more memory, in my opinion 1 gig is not sufficient it needs 2 if you are going to play games. Not a major problem as RAM is not that dear.
I don't know. If I had the money I would be tempted to get the Medion because its closer to what I would want, it comes with 3 gig of memory and a 8600GT graphics card which is fairly good. I've never had a Medion so am unsure if their build quality is on a par with Dells or not.