How far will 1GB of VRAM go?

1Gb is good till you up to x1400's

1GB is just now starting to be not enough at 1080p in some games, but only on fast cards.

2GB is a complete waste on a relatively slow card like the 7770. You're better off on the 1GB 7850, by far.

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Perfect answer I would choose you as best awnser more Vram on a slower card means slower card is slower than faster card with more Vram   Thanks sir

If you mean more vram makes it slower, then you are wrong. The gpu would just not make use of it. If it were ddr3 vs gddr5 then it would be slower but that is the ram speed not the amount of ram. Of course a faster card is going to be faster.

I would save the extra $$ and get the 2gb 7850, you wont regret it. you will regret getting a 1gb 7850, 1gb not enough now, you will be running games on medium detail to keep the vram useage down. Once vram useage goes over the 1gb mark, it flows to system ram, causing low performance and stuttering because it has to load back and forward between system and vram. Having said that the 7770 is really on the slow side to be able to use 2gb vram, it wont handle high settings anyway. So i think neither is a good choice, spend a few extra $$.

to cite an example, bf3 on ultra (msaa and everything) eats up ~1.7gb. i'm sure some games can take >1gb also.

that being said, i agree that having 2gb (saw a 4) on a slow card is a waste and they are just being used as marketing to those that are not too familiar, thinking that wow 4gb it must be fast.
may previous 560ti 1gb can only handle med-hi(mostly med) settings on bf3 and it caps out at ~900mb, so anything above that setting was not helpful.
imagine if a gt630 4gb would try ultra settings.

if you could, yes get a 2gb gpu but a good gpu not a low end, otherwise stick with a good gpu with 1gb

once the new consoles from sony and microsoft arrive more games will start utilizing more than 1gb vram. so its better you future proof yourself and get the 7850 2gb