I hope you're not planning on doing any gaming with this machine. Video playback is fine however.
using it through hdmi will give you the available hdmi res's for the screen you have attached. Which sometimes will not be all if your screen doesn't play nice.
What are you planning on using it for?
I have the slower one, but other than hdd and cpu speed the video capabilities are the same.... which is to say piss poor. It's still better than the intel graphics, but playing games like COD4:MW is like playing in molasses.
But things like full HD playback is fine.
The difference is those CPU speeds won't make a hell of a lot of difference for the money. hell it wont make a lot of difference full stop.
*edit* even if you're using the mini display port it will output 1080p
I was using 1080p through mini DP to hdmi, but the tv i was using didn't play nice and would clip off some of the image, so I ended up going mini dvi to vga and it works flawlessly at 1080p. so mini dvi to hdmi will be fine so long as your screen plays nice.
The only thing mini dvi won't do it give you resolutions above 1920x1200. which is fine as 1080p is really 1920x1080