It's a subjective argument, that will always have different reasons for different cameras...
For the last 4 years i have been purely a Contour man, and my reasons are simple, ease of use, compatibility to other devices (iPhone, Mod Live etc), bluetooth, GPS, waterproof, different mounting abilities. The list goes on...
The best feature for me currently is the ability to stream live when hooked up to the Cerevo Live Shell. That is awesome.
I currently own 2 Contour+2's and my stepson (7) has a Roam.
However, i am going to step into the world of GoPro this year and get a Hero 3 Black Edition, simply because i want the mounting abilities for different uses, primarily a Quad Copter...!!!
The one thing i will comment on though, is consider the warranty when purchasing, as i have had 2 sensors shot out on Contours, and they have simply raised a RMA with no proof of purchase and simply stated to send the camera back, and within a couple of weeks had a brand new sealed in box replacement turn up with all associated accessories as well... Which is great service...
Height 5"11, Weight 200-210lbs, Born 1969
Regular Stance, Ability NOT GOOD
2012/13 114 days
2013/14 102 days
2014/15 107 days
K2 Fastplant 154, Ride DH2 158, Endeavour Vice 155, Signal OG 155, NS Evo 157 (Stolen), Flow Quantum 155