As OP says no one answer….but the inner child in me can’t help posting.
Those cheap plastic ones are a bit rubbish. Ok for flattening powdery snow over 4 inches deep but hard to steer, crack down the sides. They are light though. Converse of this is a Friend who built one out of a pallet but it’s so firkin heavy that the kids do one run and give up. See also modern posh sledges with steering.
Best flattening sledge was owned by another guy when I was growing up and was a wide (3 ft ish) bit of varnished ply that had been expertly curved up at the front. It was a good laugh to use, could cope with really deep snow and if the weather gods were kind and you got freezing conditions overnight made a for a wicked “piste” for sledging the next day.
At that point you need to ditch the rubbish plastic. The traditional alpine sledges are ok but your centre of gravity is too high to have good control. I’ve a couple of low sledges made form tubular metal (chasis and runners) with wooden slats for lying on. Light to carry and absolute rockets on compacted snow if you lie head first….just don’t hit a tree :->
https://goo.gl/images/Jud1Xh
I may have thought about this too much……