i am using 2011 MBP macbook pro (15, i7, 8gb ram, ssd) and i can say that is incredible fast even 4 years later.
(i run photoshop, chrome with 20 tabs and no glitches in traktor 2.6.8)
- i added more ram and changed drive since my last purchase.
if i had to buy a new laptop for music i would consider:
- new MBP 15 Retina (downside very expensive , no future upgrades - so take at least 8gb ram and 256-512 drive)
- new MBP 13 Retina (downside very expensive, no future upgrades - so take at least 8gb ram and 256-512 drive )
- MB air 13 (very small and light, i am sure you can run traktor full power on it). I seen many artist playing ableton live with this small ones.
- a bit weird but i still consider that old 13' macbook pro (still available for cheaper then recent at apple) is a good solution for powerful and upgradable mac. You can buy the cheapest version from apple, and add 16gb ram and 512 SSD for much cheaper then via apple (is really simple). It also has a CD Drive that can be nice to mane a backup CD-R for performances, and it can be replaced by second HDD if you run our of space. Downside (screen is not as "advanced" as new models and is heavier then retina models.
- with new MBP you can not - upgrade later RAM, upgrade HDD (hard drive)
- i am sure 100% they have at least 2 usb. (is simple macbook and not pro that has 1 usb)
i won't go to PC word, i just don't want to spend time to optimise machine, and i like OSX interface, colors. Discovering mac make me enjoy working internet, and i don't have it on PC.
latest versions of traktor could have issues, many people complain. in worst case you can always go to older version, so no worries.
i am also using not the latest version of OSX, i just don't bother to upgrade, upgrades can break things and reparing is not fun.