I would respectfully suggest that the Polaris Lounge is not worth what amounts to nearly 3 miles of walking when *A is an option, but the general answer is that the walk outside is substantially shorter and less pleasant (I believe you have to go on the curb for some of it, but I forget since I do it airside); the walk airside is long (about 2km / 1.25mi) and convoluted (back and forth along the various terminal piers).

Once airside, I would not clear security a second time just to save a little distance. On the way there, it's probably faster to walk landside and clear in T7.