Reddit mentions of MSI G Series GT70 2OD-064US 17.3-Inch Laptop (Black)

What enr4ged is saying is that the pixel resolution is what effects the FPS, not the physical size of the screen. So yeah 1920x1080 on any screen size is going to be more demanding than 1600x900.

In terms of the FPS you are going to get, as long as the CPU is decent the biggest determining factor will be the GPU. In those models the GPU is the Nvidia 765m. It's a decent mobile GPU but not the top of the line. Here's an article with benchmarks for the 765M, 770M and 780M GPUs. Scroll down to see the gaming benchmarks.

The 765m isn't going to handle some modern games at 1920x1080 with all detail settings on (such as ultra settings in some games). If you are okay with reducing some of the settings, it should do fine. Running at 1600x1080 will give better performance if you want all the frills, but I can't say whether it would still be enough (see for example the Guild Wars 2 FPS numbers on that article). Mostly it's going to depend on what games you play but it is one of the better mobile GPUs out there.

If pure GPU performance is what you are looking for, go for a laptop with the 780M. The numbers at 1920x1080 are much better in a lot of cases. The MSI G Series GT70 20D-064US runs $2000 and has the 780M for example. Although if you go that route, budget some money to swap the 5400 RPM HD out for at least a 7200 RPM HD or even better an 256GB+ SSD.

I know you don't want PC but if I were you I would reconsider because this can run circles around that mac and for $600 you will have left get your self an ipad ;)

http://www.amazon.com/MSI-GT70-2OD-064US-9S7-176312-064-17-3-Inch/dp/B00CU9GNCS/ref=sr_1_1?ie=UTF8&qid=1394238686&sr=8-1&keywords=Gaming+laptop+geforce+780M