I'd say lower. I use box squats for my lighter squats on Wendler's 531 / boring but big, and I like what they're doing for my form at the bottom. Beware of the soreness, though. Put them somewhere in your week where you'll have a day or two to recover afterward.
Are you past 3 wheels on the squat already? You'd probably want at least that much practice on your form before adding the riskier box squat.