New rig. But which one?

Hey Guys,
My dad is looking into getting a new rig.
He called me asking about the difference between:
The Dell Inspiron 620 MT
Or
The Dell Inspiron 620 ST.

He was on the Dell site( I could not find them on it...maybe my search was done wrong.)
He asked what the difference between them was, aside from price( He wants to hook up a DVI monitor, that was about the only requirement). He wanted to know the difference in the "MT" and "ST" and I told him that it looked to just be the form factor of the case. (I hope I was right in saying that.)
He's going to put a 1TB HD in it, so the HD isn't quite what I'm looking at.
Aside from the CPU's, all I see would be the case size. Correct me if I'm missing something vitally important.
It will be used for Everyday tasks( browsing the internet, saving pictures). Nothing "heavy".

Any help would be greatly appreciated.
Thank you,
Spock96

 

The processor difference is pretty significant- but if he's just using it casually it'd be a non-issue.
I think the MT has a dedicated graphics card. Anything dell I've ever had my head inside had zero room for expandability. I wouldn't be surprised if the ST didn't have a PCIE 2.0 slot to add one.
If he's only using it for web browsing and pictures, I wouldn't see why I'd have him pay for the more expensive model.

 

Thank you. I'll talk to him more about getting the MT.