fixed gear vs. single speed, pros and cons

Sheldon Brown's fixed gear page has lots of information, but he's kind of a crufty old bike nut and gets a little technical. Somebody on CL recently asked a few questions about city riding, and which is "better" - fg or ss. Since there doesn't seem to be any ss/fg/messr news today, I dug it out. Italic quotes are from the original poster.

Just to clarify, I'm really not anti-fg. Just anti-brakeless-fg (but not at the velodrome.)

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I am sick and tired of my bikes breaking down.
Buy quality parts. Buying or building a single speed will enable you to buy fewer parts, so you can buy better ones, and there will be less to break.

What is diff b/t fixed and single?
I don't understand how you could have read sheldon brown's site on the subject and asked this question. A fixed gear means your pedals are always moving with the rear wheel, i.e. if you are flying down a hill, your feet will be spinning like a frog in a blender. You can use your legs to slow the bike, stop, and do wacky tricks like a track skid. Track racers skip the brakes altogether, and some hardcore messenger types and idiotic trendsters do so in traffic, though it has been scientifically proven that you are a moron if you don't put at least a front brake on your ride (unless it's only for the track). If you master the decelerating nose wheelie, you don't need a rear brake at all, fixed or otherwise, though if you need to do a bmx-style side-skid in the rain, a rear brake is indispensable, as the front wheel will wash out more catastrophically.

Not to get into this flamewar again, but a book called "Bicycling Science" mathematically proves that a front brake alone will stop your bike in at least half the time and half the distance (as a back brake). I've seen this discussed here before, so I expect this post will be followed by a flurry of CLers casting dissenting opinions, but you can either trust an MIT professor or a bunch of lurkers arguing about "breaks."

A fixed gear is technically a single speed (though sheldon mentions some old English 3 speed fixies) but saying "single speed fixed gear" is a little redundant, like a "two wheeled motorcycle." Generally a "single speed" is understood to have a freewheel, where you can stop pedaling and coast. Though you can say things like "I only ride single speed bikes; I have one fixed and one freewheel."

I would like to look into the idea of a single/fixed bike. Which will I want?
Nobody can tell you what you want, but if you get one with a flip flop hub, both options are open; it's fixed on one side and free on the other. I would recommend starting with a freewheel. Though fixed is fun, rewarding, and currently trendy, I wouldn't recommend it for a "newB" (as you call yourself).

freewheel:
Pros: forgiving of poor road conditions, simple, easier on your drivetrain (less breaking down if you're using cheaper parts), faster (if you consider you can ride far more aggressively: bunnyhopping curbs and road debris, superclose drafting, etc.)
Cons: mmmm, none that I can think of, though there is a certain joyous feeling you get from being unified with the road on a FG. Some inexperienced fg riders call this "terrifying."

fixed:
Pros: feels nice and pure, gives you remarkable road feel in the rain and snow (you can feel when and how your rear wheel is losing traction). If you're a badass messenger type with mad track skills like riding backwards, one leg over the handlebar track skids, one footed track stands, 180 "bmx style" skid outs, etc. then you look cooler than a polar bear's toenails. [Since I posted this, someone pointed out to me that for them, the workout is the best part of fg riding. oh yeah, Exercise, forgot about that one.]

Cons: unskilled riders can't easily pull off life saving maneuvers like: stopping on a dime, bunnyhopping glass and other road debris that you don't see until the last second, jumping curbs, etc. It beats the crap out of your knees long term if you choose to brake with your legs and not use at least a front brake (see above). If you try to look like a messenger and go to Handlebar with a brand new timbuk2 bag, a stock langster, and "messenger knickers"(tm), you will look like a complete tool and people will laugh at you. Also, unless you have some decent traffic skills (like 500+ hours on a fixed) riding in congested traffic you will ride slowly and look like a deer in the headlights.

Depending on how much you want to spend you have a few options. A $5-600 bianchi pista or specialized langster is actually not a bad place to start (note clothing tips above), especially if it comes with a flip-flop hub. I've seen them here for $3-400 from people who never quite got the hang of them. Three bills for one of those, and you'll be set as far as maintenance, compatibility, etc.

As far as "roll your own" single speed options, yes, you can build one for as little as $50-75, but there are so many things to look for. Of course, it needs to have horizontal dropouts so the rear wheel can move to take up chain slack (there are a couple pricey options to do this for vertical dropouts). Find a frame that used 700 cc wheels, not 27 inchers, or you might have brake reach issues. Then there are wheels: for older ones, can you spin the cluster off and put a $15 bmx freewheel on? (ideal). Newer ones needs spacers on the cassette. You can't just magically make an old beater into a fixie without a wheel/hub swap, and even then, you need a beefy drivetrain or you'll snap your chain or fold your chainring. Then there's chain alignment to think about. Redish the wheel, spacers, can you move the bottom bracket a few mm, or simply run the chainring on the inside/outside of the crank arm (assuming it doesn't graze the chainstay if you move it in)...you want anodized wheels (grey, surface hardened, squeak less), etc...

I've built chumbucket freewheel single speeds for $75 and totally bulletproof ones for $2-250, as well as a "sky's the limit" 14 pounder. I've heard that enterprising types have sold "messenger style" single speeds on eBay for double what they can get in the city, simply because lots of people don't know how to go about building them.

I don't want to call anyone in particular out on this board, but there's not a stellar crop here at the moment. But, for conversation's sake, san fran blows away chicago in this department. From the current sf board:

[dead links removed]
Single Speed Touring Road Bike - $230 mmm...this is what you want. Resprayed, custom 27in touring wheels, frame-up rebuild. There are currently "donor bikes" on Chicago CL for the same price, and they are still $200 away from looking like this one.

Somec Track Bike - $375. This is a $1000 handbuilt steel frame. F*#^ing Brilliant bike for the price.

and here's what you don't want:
Bianchi Pista $625 This should be $350-400 max. This douchebag has tallied up almost every nickel he's spent on this 3 year old unridden bike, and wants it all back. I'm surprised he's not charging for the air in the tires. Newer models (from sheldon brown) come equipped much like this for about the same price.

That's all for fixie/ss 101. There may be a pop quiz.