Very few machines today have a hot/cold fill. Most are cold fill only.
With a hot/cold fill heat is lost in the hot water pipe so unless you have a very short run of pipe to the washer it will be mainly cold water going in anyway. Then the hot water in the pipe will go cold whilst it's sat there.
I think, because of this, that the cold fill only will be the most economic.
depends if you have to heat the water for it ?
if you have hot water on constantly for family use then yes get hot / cold fill.. if not a cold fill would be more economical as it only has to heat a small amount of water in the machine,ours use very little water compared to the early washers
and if you go visit your daughter in the middle of the bush in Africa where they only have the facilitity for very, very hot water to be connected to the washing maching - everything comes out a fairly uniform colour and five sizes too small.