Hi Stano
I have noticed this too at times. One factor is simply that one TV is closer to the antenna than the other. It's strange depending on your proximity to stations. (Sometimes) the TV furthest from the antenna works better. Literally because the length of cable from antenna to TV is longer on say bedroom TV, and the cable itself acts as more antenna believe it or not.
I have rarely had all of my TVs ever bring in the exact same amount of antenna stations at the same time. When I'm in a more remote area, it's always one or another of the TVs that does better than the other ones. Close to a city broadcasting 45 over the air channels all TVs kick butt pretty good.
Hope I'm helping not hindering....take care, and thanks for your service to our country.
W.D.