I have had my MBP 17 for over a month and had it on Better Battery mode and I just switched to Higher performance, since I am new with this computer is there really a difference and if so what are they?
Yes, there is really a difference. The Higher Performance setting uses much more power, generates a lot more heat and fan noise, and if (and only if) you're playing 3D action games or doing other 3D rendering tasks, it will give you better performance. The rest of the time, it's just a really good way to run your battery down fast. And of course Windoze uses the faster GPU, if you run it in Boot Camp. So running Windoze in Boot Camp is another great way to run your battery down. Keep your AC adapter plugged in if you're going to use the Higher Performance setting.
In Higher Performance mode you are using a different GPU - the 9600 instead of the 9400 - and it's possible for both GPUs to be used together to improve video and graphic performance. There's also a potential difference in memory usage. The 9600 GPU has dedicated video RAM while the 9400 GPU uses shared RAM, that is part of the physically installed RAM. If you switch to Higher Performance then restart the computer you will recapture the 256 MBs of RAM shared with the 9400 GPU.
As eww has said the 9600 GPU has much higher performance capabilities, requires more power, uses additional dedicated RAM, and therefore generates more heat and consumes more power from the battery if you operate off the AC adaptor.
