It's not harder, just preferred by most sound technicians. True, it gets a better sound, and a lot of sound engineers are used to having the "vent" in the resonant head; but it's not harder to mic it up. A lot of the time, you'll get asshole sound guys that expect every band at every show they work to be the same. But every once in a while, you'll run across a sound tech that's also a musician; or even better, one that is also a drummer. Those types of sound guys are a diamond in the rough, though. It basically boils down to your own personal preference. If you like the sound of your kick without the vent, more power to you. And it's not really the sound technician's responsibility to tell you what sound YOU like. I've been a sound engineer going on 12 years now and I can tell you that shows run a whole lot smoother when the production team just does what the band asks. Next time, just tell the guy to put the mic dead center of your reso head, about an inch away, roughly about where the beater on the batter head will hit. That way you get a good punch and resonant tone. Oh, the sound guy should also know that a unidirectional mic is optimal for the kick rather than omnidirectional. Omni's are best suited for overhead mics.
The vents provide more attack than anything else so that's why it sounds better. Personal preference man. That's all it is.
Oh, I don't have a vent in my reso head either, and I'm quite happy with it.