which of these comes out on top(if any)

I have a WD 500gb External ive been wanting to change for a small/mini pc to connect to the tv and store my movies as i have loooads and music and use it as abit of a HTPC and keep my hard drive as back up(does have nearly all my files backed up on it already)..

so looking online ive so far seen 2 that are used and no set price as on auction, but have decent specs, however i cant tell from what ive been reading if they upgradable as the sites ive gone one for info seems to be from america lol..

the 2 ive seen are:

Acer Veriton L480G
Core 2 Duo E5300 2.6GHz
2GB DDR2
320GB HDD WINDOWS 7 PRO

(4gb ram max and from the description 320gb is max though ive seen higher unless american version )

Dell Zino HD (spec given in desription)

Athlon 64x2 1.50ghz
4gb Ram(8gb max)
500gb
Win7 HP

i like the look of these and from brief youtube videos they are of ideal size, however i cant see what options the Acer has, but the Dell can upgrade to 8gig and i think 3TB going by crucial which i like, not that i need 3TB, above 500 be nice due to my movie collection..

im still browsing, but the only alternative(only new one aswell) i have to these or any other is the Zotac Z-Box SD-ID12 which sounds really good and looks very sleek..

but as my titles says, which of these 3 listed if at all, would come out on top?