Lots of blackberries and birds!
I planted my hedges nearly 20 years ago now. Money was tight then as I had a small family so I only bought small 8" to 12" hawthorn, field maple, dog rose, etc. people passing said it would never grow. But they were wrong and the hedges are nowNiall an thick and in great shape; a haven for small birds and for the past few weeks an endless supply of blackberries, right outside our back door.
It grieves me to see people on our estate grubbing out the old privet hedges and replacing them with timber fences that last for only a few years before they need reprinting and patching up. I really believe that a hedge that is cut just a couple of times a year is less hassle than a timber fence. If you have the room and the inclination, I say go for a proper hedge.