SD series has the on screen camera compass, water temp, water depth, voltage, bigger battery, free camera panner, 4:3 aspect ratio, longer camera cord (debatable if this is better). I “think” the screen resolution might be a little better, but not positive..
I’ve owned all of the Marcum camera’s, the VS825SD is by far the best and worth the price uptick imo, but I would buy used over new…I’ve never purchased a new one, you can tell right away if what you’re buying was taken care of or not…if you must buy new, then the 485 will work just fine…
I purchased a like new VS825SD last spring for $200, so deals are out there, you just have to pounce on them fast as many other ice fisherman are watching for them too…