Got mine as a freebee with sled.
No problems with them moving or falling off (maybe previous years this was a problem)
Haven't noticed any problems with snow building up on them
However they do help hold some snow\ice chunks in the belly pan. Inside face of protector acts as a bit of a dam sometimes and prevents snow chunks from sliding out of belly pan....sometimes.
There are pros and cons to everything, I like the fact that they skip over stumps, rockts, etc instead of snagging the A-arms.
Price may be a little steep but so's the damage that can happen if you hook something.
Just my 2 cents