look into video card overheating problems with it. google it. all mac with dedicated video have this problem. in 2yr or so they break up.
BTW if you don't go the MAC route, make sure to check Lenovo. They have the best keyboard I have ever used on a computer (laptop or desktop). I have a ThinkPad E530 15" HD+ (1600x900), 16GB RAM (officially supports just 8GB but in practice works just fine with 16GB), I7 CPU, 256GB SSD + 1TB HDD (in caddy, replacing internal optical drive). Only weak point is video card - Intel HD 4000 - but I got this model because I'm using linux so i'd rather have this with 16GB RAM and i7 for VMs than a i5 and good video card with I don't really need.
If you want long battery life and are ok with a 12.5" screen, check out the Lenovo X240 - it does like 16 hours on battery or something like that.
In the end, the most important question is what software you plan to run on it. Windows has more apps, most SEO tools are for windows, etc. So don't forget to think at what you plan to use it for.