Where are the losses in a Ladder-
Line fed system? ....

The tuner that is usually used offsets the advantage
of the line itself. Sure, on paper you shouldn't really
be able to notice it. But I do when I test it. It's actually
measureable on an S meter when doing A/B comparisons.
Or at least it was for me when using a 989c tuner
and minimum inductance vs coax fed.
That tells me the tuner loss can often be a bit more
than it's cracked up to be. But I also found if you don't
use the minimum inductance when tuning the tuner,
you can lose quite a bit. I saw easy 20 % losses when
testing that one time. If I used the very least inductance,
I could get it down to an almost unmeasureable level.
If I get on 80m and want the very best efficiency I can get
feeding a dipole, I use coax.
Of course, the line is never more than 100 ft.
Usually more like 50 ft. I have a 50 ohm radio feeding a
low loss 50 ohm line, to a 50 ohm antenna feedpoint. You
have uncluttered perfection. :-) And in the real world
the most efficient that I've seen so far. If there was better,
I'd be using it. I could see using the ladder line on real
long distances. On the higher bands, it could be noticable.
But like I say, my run is about 50 ft. Considering efficiency
vs ease of use, wx resistance, ease of lightning protection,
coax is a no brainer for me. Of course, I ain't everyone.. :/
MK