It is absolutely not better to be 100% utilized. The math at the end of this comment suggests that the difference between 100% utilization and 50% utilization is marginal, but the real pricing difference you're playing with is probably something closer to 2.5x-3x the rate you think is competitive. It is better to be 50% utilized at 2.5x what you were making at the rate that had you 100% utilized.
It's actually bad to be 100% utilized at all; if you are, you're treading water building your business. When you exceed 80% utilization, do one of two things: raise your rates, or start hiring.