I preordered a 13" MBP with TB after the Apple conference 2 weeks ago. These are the specs I got: 2.9GHz dual-core Intel Core i5 processor Turbo Boost up to 3.3GHz 8GB 2133MHz memory 512GB PCIe-based SSD1 Intel Iris Graphics 550 Okay, so I don't know much about GPUs. Portability is not a huge concern as I have a 12" MB and could rock that for when I am on the road. I have just preferred smaller notebooks, which is why I went for the 13". The most power hungry tasks I will be doing are occasional video editing and playing ZWIFT (does anyone know what this is?). Basically, an online cycling MMO video game, but instead of using a control pad, you use you turbo trainer and road bike. Anyway... I was thinking of cancelling my order and going for a 15" with the following specs: 2.6GHz quad-core Intel Core i7 processor Turbo Boost up to 3.5GHz 16GB 2133MHz memory 512GB PCIe-based SSD1 Radeon Pro 450 with 2GB memory I think the price difference is around £500. Will I notice a huge performance boost for 4k video editing and gaming? And how much of a difference is there?