Which one to pick is highly dependent on the bike.

Vintage touring bike? Cantis are likely the only thing that will fit.

Using a rim that is noticeably wider or narrower than the bike was designed for? Smooth Post Cantis will handle it better.

Want the best possible brake feel? The best brake levers are usually short pull.

Want more modulation? Cantis.

Mud clearance? Cantis.

Fender clearance? Depends on the bike, Cantis and V-Brakes are both capable of being in the way on a few bikes, and swapping to the other type can be a solution.

Want the easiest brake to set up? V-Brake.

Want to cheap out on your brake and still have it work well? V-Brake.

Want a brake that doesn't stick out and hit your heel while pedaling? V-Brake.

Having issues with squealing or shudder due to a headset mounted cable hanger? V-Brake will fix the problem.

Want the most stopping power? V-Brake, though high end Cantis can be comparable if set up well.