hokiefyd 

I haven't been satisfied with the sets of mechanical discs I've tried. :-( I have a pair of Avid BB7s (which are usually cited as the best of the bunch) and some cheap Tektro ones similar to what would be had on one of these hybrids new. The BB7s are definitely the best of the ones I've tried, with the feature to adjust both pads at once. However, most mechanical discs seem to have a fairly narrow range in which they work correctly. By that, I mean there are definitely many ways to set them up, but (like traditional cantilever brakes) there's definitely a "sweet spot" in terms of operation. I have found that moving the caliper itself so that the disc is right up against the movable pad, and then adjusting the fixed pad all the way to the left, produces the best result. Of course, you continually have to re-adjust the calipers as the brake pads wear. Except with Avid BB7s...where you can adjust BOTH pads, obviating the need to adjust the caliper body itself. If I were using mechanical discs, I would use only the BB7s (which would have to be purchased separately from the bike, as only higher-end bikes come with those stock). There are some newer designs (like Tektro Spyke) that actually move both pads towards the disc, like hydraulic brakes do. I haven't used those, but they sound pretty neat.

The thing I like most about disc brakes (all types) is the consistency you get in braking power and modulation. Rim brakes are subject to a bunch of different environmental and mechanical variables. If there's any amount of rim surface runout, you'll feel that either in the brake lever or in a pulsing feeling when braking (similar to a car that needs its brake rotors resurfaced). I've also found that differences in humidity can really make them squeal. I keep all my bikes in my shop in a walk-out basement and my rim brakes will squeal for a while after taken out on a humid day because of the sudden change in humidity.

There are definitely pros and cons to both.

Cheers!