Continuous Advance Priority AE on the Mode Dial allows the camera to shoot at its highest frames per second (fps). In Automatic Auto Focus (AF-A) or Continuous Auto Focus (AF-C), the shutter speed is automatically selected by the camera and the aperture is set to the fully open position of the attached lens. In Single Auto Focus (AF-S) and Manual Focus (MF), aperture can be manually selected, but the camera controls the shutter speed automatically.
Hi/Lo Continuous Shooting in the Drive Mode settings gives you the option of selecting a high or low fps speed, whichever might best suit your purpose. The Hi setting shoots up to 8 fps. The Lo setting shoots up to 3 fps. You can adjust both the aperture and shutter speed manually when the Mode Dial is set to the P/A/S/M modes or automatic settings like the AUTO or AUTO+ options.
In summary, Continuous Advance Priority AE can shoot at a higher fps than Hi/Lo Continuous Shooting, but with slight limits on aperture or shutter speed control since the camera chooses those values automatically for you. On the other hand, while Hi/Lo Continuous Shooting may not use a higher fps than Continuous Advance Priority AE, you have more flexibility for controlling the aperture and shutter speed.