How much better is a dual-graphics card laptop?

DUAL GTX560M (1.5gb x 2) vs. GTX560m (3gb)

How different is the gaming performance with these two laptops?

Specifically I'm looking at this Asus G74SX vs. Sager NP8180

ASUS G74SX-XR1 - Gaming Laptop
Sager NP8180 (Built on Clevo P180HM) Custom Gaming Laptop

 

Theorically 2x 560m should give you roughly the same performance as a stock 485m/580m, both are high end cards.
A single 560m therefore performs at least the half.
Sli is a good tech althought it still need time to completely stabilize.
Most common problems are missing sli profiles for newer games, stuttering, negative scaling (usage not completely reparted on both cards).
Also add the fact that not all the games support sli and sli works only if it's both driver level supported and game supported.
There are techniques to get sli working on games that doesn't support it if, as an example, they are built on a game engine that used it in another game (such Ue3).
Compared to amd crossfire, nvidia sli works wonder, is more stable and less prone to problems.
Also having a sli system boosts up those nvidia specific features such cuda processing, Physix, Sli antialiasing, things usually not possible (performance wise) on single cards.
Remember however that 560m nowadays are considered medium end cards, and they begin to show their age with modern titles. Sli will without doubt help, if supported.
My advice is unless you go sli with 2 powerful cards (such 485m/580m) dont go sli with 560m at all.
Spend a little more and get a single fast card now and save the hassle.
I had sli systems (xps m1730, 2x 8800gtx on my desktop) but I've gone single again lately and I don't miss sli at all.
I was wasting time into get sli working in newer titles than actually play them, and sometimes, I was forced to not use it to avoid problems.
Hope it helps.

 

I guess I'm lucky for never having to argue with my sli cards, I'd say get the dual card solution. Sli 560m are much more powerful than a 3gb 560m, 3gb won't even be utilized fully and is just a marketing gimmick. Sli has really come a long way to improving sli performance to almost double a single card configuration.

 

If you don't know what you're getting into with a dual gpu setup, then it's best to stick with single cards. Dual gpu's, especially in laptops are for extreme enthusiasts only. If you haven't tested atleast 3 different drivers on your current machine in the past 30 days, then stick with single cards.

 

I really don't think testing different drivers is all that relevant. I've used 1 driver on my notebook since I bought it (whatever the most up to date one was at the time) and it runs perfect.

 

Just in case you did not know

1.5GB GTX560M (single) = 3.0GB GTX560M (single) in performance.

There will be no difference between the two.

 

I posted this on a different topic, but I only got one response, so I'll try again here: will 3gb vs. 1.5gb not make a difference two years from now for games released then? I know there's almost no difference now, but what about in the long run when new games are released? Or does it not matter because the GPU bottlenecks the ram anyway?

 

Sli came out 6 years ago. I don't think it will mature any more.

 

yeah I agree with above

 

In the long run when games are using more than 1.5GB of ram the card will be too slow to game with, either you will have to turn down the settings (thus you will use less ram) or the resolution (thus you will use less ram).

 

^ That is true taking into account IF the GPU can use more than 1.5 GB or RAM ...

 

Added weight / battery life loss / size / heat was never worth it for me for 10-20% more fps.
It suddenly goes from notebook size to nettop size lol.