What do you guys think about these two computers?

eMachines ET1810-03 Refurbished Desktop PC - Intel Pentium Dual Core E2210 2.20GHz, 3GB DDR2, 320GB SATA, DVDRW, Windows Vista Home Premium, White at TigerDirect.com

Dell Optiplex GX520 Desktop PC - Intel Pentium D 2.8GHz, 1GB DDR2, 400GB HDD, DVDRW, Windows XP Pro (Off-Lease) at TigerDirect.com

I'm thinking about buying a refurbished pc that has more memory than mine but I dont know anything about brands or anything. You guys are smart so tell me what you think, are they good or bad and which ones the better?