We use concrete bunks for the animals we are backgrounding. Have only been using them for grain. Biggest drawback I see is having to shovel them out every time there is a significant snowfall.
I’ve used fence line bunks and heavy portable steel silage bunks. Basically you need a cement apron along the fence line bunks. I wouldn’t go back to fence line bunks except for intensive feedlot conditions. Too much snow and waste shoveling. Also figuring the cost and losses (to dust ect) of processing feed, try and get the cow to process it. Sometimes processing low quality feed with good feed costs more than you think.