I have AQ hdc318's that I've used both slots and aero's. Hands down the aeros are better. The biggest two differences is air movement and resonances. I am louder with a little less power with the aeros tuned to 32hz and the slot was 35hz. Slot ports tend to have nasty resonances at and below tuning. You get none of this with Aeros and when you play at or below tuning it is as clean of a sound as any other frequency. The other big difference is the air movement. Even with less port area you can feel the air movement in the front seats of a large SUV using aeros, which is not the case with the slot. In my experiences aeros are better in every aspect and well worth the cost.
Bought from - Hazardous0388 (4 db Drive 2000.1s), Psychoacoustics (4 Powerbass XA 3000'ds), and blackedoutavy (PPI A200)
Sold to - D-Rew (Knu 1/0), d77543020 (Knu 1/0), F1McLarenAGR (Audioque 4x90), and SacTownBully84 (Knu 1/0)
Traded with - SacTownBully84 (my xa3kd for his xa1.5kd + cash)