I asked my rigger, "Why don't you use a loos gauge to test the rigging?"
He said, "In my experience the accuracy is marginal. If you were racing the boat in might provide a smidgen of difference, but not more than I can feel when I grip and release the shrouds."
Before I left on my trans-Atlantic crossing, I had a professional rigger inspect my rigging, and tune my rig as I felt it was an area I had insufficient knowledge. It was done in much the same way as you describe. I also asked that same question of the rigger and received the same answer.
I then almost lost my rig in the middle of the Atlantic running down the edge of a major hurricane.
Why? Fundamentally because the rig was not tensioned properly.
I ended up having one of the best riggers in Europe inspect and correct my rig and they used a Loos gauge. Given the size of my rigging, it's really hard to "feel" the correct tension.
I think on a smaller boat, this "feel it" may well work, but once your rigging gets over some size - not sure what that would be - I think you have to use some method of measuring the tension.
When you go take your boat out for a test sail and then "feel the rigging" - are you really testing for all wind conditions? I don't think so.
If you aren't doing a major trip, and you have the luxury of time and multiple sailing trips under various wind conditions, then the "feel the rigging" option will work fine. But if you are heading out and want to know if the rig is right from the get go - use some form of measurement technique - be it a Loos Gauge or the yard stick method or another method that gives some form of measurable output. Get it right the first time.
dj