Total personal preference. Both are excellent subwoofers and are hard to describe when comparing. I personally prefer the ID Max, but that's my subjective opinion. I feel the ID Max really shines in the midbass transition area, and low frequencies are very accurate as well. The X.X.X. has good transition as well, and opens up at lower freqs, it's a little more authoritative down low than the ID Max is and sounds great doing it. X.X.X. is also a louder sub. It's all in what you like.