Aldi Medion: Intel Pentium 4 2.66GHZ processor, a 120GB Seagate hard drive at 7200RPM, Samsung 256MB DDR RAM, 16x DVD, a Sony CDRW drive, a 128MB DDR GeForce4 8X AGPTi4200 graphics card, and a very cool media port.
The Dell has a much better Processor and motherboard/chipset. The extras may be less like the HD and no CDRW but those can be bought seperately for cheap and I wouldn't buy a 120 gig 2mb cache seagate anyways. As for the vid card, the GF4 8x 4200ti is nowhere near as good as a Radeon 9800.
Lets looks at the prices of some major parts alone:
Aldi: P4 2.66/533 fsb $180
Dell: P4 2.8ghz/800fsb w/HT $300
Aldi: GF4 4200ti 8X $100-120
Dell: Radeon 9800 $300-350+ (low estimate cuz it's a non retail model but its better then a R9700 pro and they still sell for $300)
The Dell motherboard is much much better too with onboard 2 SATA ports and Dual channel 400mhz DDR/4slots.
The aldi machine is a nice deal for $699 and maybe good for a home user newbie who doesn't want to go into their computer to add parts. This dell is is alot better computer though at it's foundation then the aldi which is based off medium end technology thats going to be off the shelves soon. The Dell has top of the line technology that just hit the shelves. The Dell may not have as many little extras, but all that is easily added for cheap. Its also cheaper then the aldi rig by about $100 and you don't have to go physically to a store and pay in cash. I think the choice is clear.