Without bags (other than a backpack) it takes me 15 minutes from the UC to the *A lounge, and I know exactly where I'm going and I walk fast. Dragging a roller-bag adds at least a few minutes to that (depending on how busy the terminals are).

Land-side the walk is definitely faster, although not as much as you might think as it too can be very chaotic with peoples/bags/skycaps/etc cross/blocking/etc. By the time you add in the effort to actually get landside (which involves walking back through the security area), and then going through security the odds of it being faster are pretty much zero - although it will be a little shorter distance to walk (but not much).