Reason not to go with a Mac?
TBH, there's absolutely no reason to ever go with a Mac unless there's Mac-specific software that you must use.
Mac owners don't like this topic because it hurts them where it does count but cost-wise, you can always get more machine from other systems other than a Mac. OS choices are plenty and there's many other choices besides Windows and OSX that you could use on that machine.
Run Windows on Bootcamp... sure you can do it but it's not the same as using a true PC with Windows. Bootcamp drivers aren't always very good. It's always better to run Windows on a true PC and it's always better to use OSX on real Apple hardware than on a Hackintosh.
GPU, many complex apps can make use of both your CPU and GPU very efficiently aside from games. Macs are often hampered by using mediocre video cards and touting themselves as "king of graphics platform". That's like someone in a Honda Civic claiming to be king of muscle cars because it has VTEC.
Keyboard layout on a Mac is inferior. Having to rely on a Fn button to access normal F keys, not having a built-in numberpad, no Home/End/PrtSn keys, having to use 3 sometimes 4 key combinations can really hamper productivity. We did a study back in 2010 testing to see which users would produce more in an enterprise environment and Windows users always came out on top. The keyboard is no different across all Macbook products.
USB ports on a Macbook-anything are poorly spaced and implemented. Granted it's not an issue exclusive to Macs but they put the ports so close together that it's quite often where you'd have to carry a separate hub or USB extension just so you can fit 2 flash drives side by side without interfering and there's only 2 of them. PC laptops come with 3 on Netbook-class machines, 4-6 on higher models. The 17 inch MBP with only 3 USB ports...
You have to dish out $30 or more to buy an adapter just to connect your MBP to another external display. Most sub $500 PC notebooks now come with both HDMI and VGA ports.
Glossy screen and glare. Many laptops use glossy screens because they look prettier but while this is a personal preference of mine, I prefer Matte screens.
Screen resolution, Macs use some of the lowest native resolutions around. 1280x800 on the 13inch model... my Netbook supports 1366x768 and it's noticeably sharper and cleaner on HD stills and video on an 11 inch screen.
Firewire port... who the heck uses this? 1 person out of a thousand? Video professionals? Yeah, because every Mac user is automatically a video professional...
No Expresscard slot but on the 17 inch model.
Despite all this I love my MBP 13. However I own Thinkpads to quench my PC needs. I don't see why you have to have everything in 1 machine, I prefer to diversify, use OSX on a true Apple machine and use my Thinkpad for everything else.
Unless you're one of those Alienware type folks that much have the highest benchmark scores and play every game at the highest settings, you won't be disappointed with any MBP. To me, they're a lot of fun to use.