I wouldn't say that the bulbs break easily, or that Surefires are not durable. BUT, incandescent bulbs in general definitely break easier than do LEDs. Any LED will be more durable than an incandescent bulb. But then there is the exterior of the ligth to consider... how beat up will it look after a few years of EDC?
Well, I've got a few E series Surefires, and I've had a few Arc LSs. From what I can tell, they're finishes are equally durable. I have yet to need to replace a bulb in a Surefire, but I also know that the time is coming, and I have spares at the ready. If I knew I'd be dropping the light regularly, I'd narrow my choices to LEDs.
And as for the light quality, it is very difficult to compare a great incandescent and a great LED light. The Surefire will throw the light MUCH further, but the LS is far more useful for near-field tasks. If you're searching for an object in an open field, the SF would be best. If you're looking for something in the bedroom, I'd grab the LS. For things like working in enclosed areas (under the dashboard of the car, under the sink, etc) an LED light is superior, in my opinion. But for now, incandescents still have the edge for distance illumination.
Oh, and I almost forgot the official CPF response: Get both!