New Army Pass is about the same distance -- the difference is negligible. "Old" Army Pass tops out about 300' lower elevation, so that is the main advantage.
Since it looks like you're planning a Langley trip, let me encourage you to take the no-longer-maintained South Fork trail. I think it saves a little distance compared to the CW Lakes trail. I took it 2 years ago, and missed the junction, and got off-route only one other place (approx here
The junction off the main trail is here
, 50 yards after it crosses the creek. It is little used but easy to follow. Here's where it re-joins
the maintained trail by the South Fork Lakes.
If you would like more gps markers, let me know. ...You could make a loop hike -- south fork trail and New Army on the way in, old Army and the main trail on the way out.