The CardsThe first picture is always the GTX, the second is the GTS.
Both cards are very similar in design and use the same cooler assembly.
In order to handle the increased heat output, both cards use a two slot cooling solution.
While the GTS has only one SLI connector, the GTX has two of them. This allows the GTX to be used in more advanced future configurations like three cards (one for Physics).
Looking at the cards from top down you see that the GTX has two PCI-Express power connectors. This move was necessary to make sure that the card does not exceed the 75W max. power draw from the connector. Here you can also see that the GTX is a bit longer. The total length of the GTX is 10.5" which should fit all normal cases on the market. The power connectors are now 90° rotated to allow for better cable routing in the case.
Both cards share the same output configuration. Two DVI connectors, both are dual-link capable.