In some quarters Biggar is perceived to be in the box seat having spent an extra week with the squad however Hook's absence - to turn out for his French employers Perpignan as they beat Clermont Auvergne - is viewed as a factor in his favour.
Neither player had much opportunity to strengthen their case in the autumn with Priestland starting three of the four matches, all of which ended in defeat.
Despite their lack of recent experience however Jones is adamant Howley's headache is not one he would relish.
"It's fiercely contested at the moment," said Jones.
"It will be a difficult one. I know that the coaches are mulling it over and reviewing training quite a bit.
"[It's about] trying to select with Ireland in mind as well as our own style of play as well.
"Both players are doing well. Dan had the extra week by Hooky being out in France, but of course Hooky had a game.
"It will go right down to the wire, I'm sure, for Rob [Wales interim head coach Howley]. I'm glad he is making the decision not me."