Extremely difficult to see unless they're turning?
What do you suppose gliders do for probably 90% of their flight time?
This is a debate you'll never win because pound for pound glider pilots are better airmen than power pilots!
About a quarter of the members of the gliding club I belong to are airline pilots who only fly powered aircraft for money or as a tug.
So you're actually saying you can't see on a map where there's intense gliding activity?
Or is your understanding of meteorology so poor that you don't know how a cumulus works?
Glass fibre designs have that aforementioned disadvantage caused by heat but what is the basic colour of the vast majority of the GA fleet?
Gosh! Its white with a couple of go faster stripes, isn't it?