Some people say you can't gain muscle in a caloric deficit. But the amount of muscle you gain depends on a lot more than just caloric intake: how advanced you are, how much time you have to train, how much rest you get, how you eat, and how big that caloric deficit actually is.
Eating right, training, and recovering properly are the most important factors in gaining muscle, and as long as you're not in a huge deficit (more than 500 calories) you can still make gains. It's possible to build muscle without also gaining fat. And contrary to popular belief, it's even possible to lose fat while building muscle.
But won't the person who eats a caloric surplus make more gains? Yes, but probably not by as much as you might think. And for the "dirty bulker" or the guy who's fine with gaining just as much fat as muscle, when it comes time to cut, he'll often find the extreme change in diet stressful both on the mind and body. He might even start losing muscle during a cut or develop metabolic damage.
A Better Way
Over the span of a few years, the lifter who eats a sensible diet at or around maintenance level calories will likely make better gains than the individual who's constantly switching between bulking and cutting cycles.
I'm not saying that bulking or cutting don't have a place. Some people find that bulking even helps them overcome training plateaus. But bulking and cutting should only be used temporarily, not long-term, and they're not necessary for everyone. Don't use your muscle-building goals as an excuse to pig out, and don't use your fat loss goals as an excuse to catabolize muscle.