1GB is quite fine. But you may want the bigger HDD just because.
6770m is slower than the desktop version, probably only equal to a desktop 8800GT or at most a 4770 in performance, and you'd never be able to properly utilize more than 1024MB on one of those, I'm certain.
Having lots of RAM on a video card is a sales gimmick because most people think "More is better" is always true.
Generally speaking, you do not need more than 1GB of RAM if you are using up to 1920x1200 resolution. Above 1920x1200 resolution it is recommended that you have a 2GB video card because more textures are loaded into memory in games.
At also depends on how powerful the graphic card is. A weak video card can be too slow to use all the available RAM regardless how much there is. For example, the desktop Radeon HD 5670 512MB and 1GB versions basically have the same benchmarks, at 1920x1200 resolution and above the 1GB may get 1 extra frame per second. This basically means the Radeon HD 5670 is too slow to make use of more than 512MB of RAM.
That would also means a Radeon HD 5450 1GB will also be too slow to use all 1GB of RAM, but the 1GB is an attention grabber and people may simply buy the card because of it.
I know you said the hdd is 200gb more but what are the sizes. More hdd space is always desireable and other than the extra 1gb of vram are all the spec's the exact same on the video card , people are always saying that you will never use more than 1gb of vram but the manufacturer put it there for some reason and since we don't know what games will come out and what apps will come out I would always take the extra vram just because you never know.
Well, I can buy an external HDD later if I need too.
As 'Inzone' said, manufacturer put the extra memory for some reason, I am wondering the same. But as others have said more than 1GB for that card would not be utilized and is a marketing gimmick. Does the extra 1GB of memory have absolutely and totally no effect other than just 1 extra fps?