Are Slicks More Prone to Flats?
Are slicks more prone to flats than MTB knobby tires?
That totally depends on tire construction. True slicks, also called a baldies, with 0 tread can be more prone to puncture flats as they are often very lightly constructed. They are also quite treacherous when things get wet, but that's another issue. A knobby MTB tire can be every bit as prone to puncture flats as a baldy if they are lightly constructed as well. The only advantage they have is the knobs do keep the tread cap slightly elevated off of the riding surface. So it takes a bit larger object to make contact and penetrate the casing.
The ideal tire for commuting on an MTB is something like the Schwalbe Marathon series, Continental Contact series, Panaracer Ribmo, Cross Town, or Pasela tires and their like. All are good examples of pavement specific commuter tires. Most if not all have an additional belt of thicker rubber or other material to increase puncture resistance. They also use a bit harder rubber compound in the tread area which greatly increases the longevity of the tire. Also most of these tires have a sipped non-raised tread patter that adds almost 0 rolling resistance, but helps a bunch when things get wet. Things like rail road tracks, man hole covers, painted traffic lines, or very smooth asphalt can become very slippery when wet. While you still have to slow down during wet conditions, the sipping can often make the difference between staying upright and landing on your butt.
Anyway, the short answer is, no, most baldy or slick tires are no more resistant to flats than a knobby.
"I do whatever my Rice Cripsies tell me to!"
The raised knobs of a knobby tire do better with things like goatheads, because IF the goathead gets into a knob, sometimes the pokey part is just too short to get all the way through the tire before the 'head' bottoms out on the knob. And if the goathead gets into the space between the knobs, sometimes the knobs are tall enough to keep your weight from sticking the thorn all the way through. ...millions of variables though.
I am 100% sold on tubeless for the commuter, based on a long history of flats due mostly to thorns, and zero flats since I switched. Knobby or not, if you are running at tire that can be set up tubeless (and most tires can), you owe it to yourself to try it.
I'm using Schwalbe Big Apples (which are seriously beefy slick-ish tires that you might consider trying...lots and lots of puncture resistance, but you pay for it in weight), and Michelin A/T knobbies on my two bikes, both set up tubeless, and I'm very happy with both.
You have no excuse for driving to work
(unless you don't have studded tires)
(no excuse for that either)
A lot of MTB tires don't bother with puncture protection because the kinds of things that put holes in tires on the road are not really present on the trail - stables, glass, random bits of metal. If a slick tire is constructed the same way, or you get the cheapest slick tire you can find, you're going to get a lot of flats.
Almost all road training/racing tires have a puncture-resistant layer. The specifics vary, but it's usually some kind of fabric. I actually have the best luck with my Continental GP4000s - the tires on my road racing bike. It has something called "Vectran," which is probably just a trade name for a slightly different formulation of nylon, or maybe something a little like Kevlar. However, I've also done fairly well with a Forte, which I think used kevlar, and a Specialized Armadillo. Currently, my commuter has a Michelin City tire, and while I haven't had any flats (knock on wood,) it hasn't been on the bike that long - couple of weeks, maybe. I had a Kenda Kontender that got horrible as soon as the rain started this spring, and then got a tread cut. I was a little relieved to have an excuse to throw it out.
It's impossible to find any good data on the effectiveness of one tire or another in avoiding flats, because it's not really in anyone's interest who can afford to do a good experiment and the anecdotes you can find on the 'net are just that. My own thought is that all the breaker belts in tires that have them work okay, and better ones are more likely to be in tires the company positions as training tires for someone who spends $60 on a tire. Figuring out which ones are training tires and which ones are racing tires is hard, though, because marketing people call training tires racing tires. I'd say if it has puncture protection and maybe says something about high mileage, you're good. There are a few slick tires for mountain bikes that are built that way. If you have disc brakes, you can also build a new wheelset with 700C rims and get the whole range of options, but honestly once you're looking at buying anything to improve your commute, you may as well just commit to the project and buy an old 12-speed on Craig's List.
I think slick tires are actually better for traction on the road. They provide more consistent grip and have nothing to squirm vs. knobby tires. It's also nice to have lower rolling resistance. But, I haven't used my MTB as transportation in a very long time. I have a cheap road bike that does that job, so knobbies aren't really an option anyway.
"Don't buy upgrades; ride up grades." -Eddy Merckx
It would be fun to do a Consumer Reports type test with various tires ridden purposefully through a set course of glass, nails, and other hazards, all with the same bike, rider, rims, tubes etc.
I put 3000 miles on my Schwalbe Marathon Plus' with no flats and then gave them to my buddy and he has a few hundred on them. I live in Colorado and was getting a couple of flat tires a week with slime tubes - Damn Goat Heads!! I got rid of my 26er and now have the Plus' on my 29er running them as tubeless with zero flats in 400 miles this year.
The below link has some good post about the Marathon Plus tires - click on it and scroll down a little ways and read away.