As both games are pretty much the same type the question is would GOW4 be a better game than HS2 - and based on previous games I would say yes and hence I would prefer GOW4.
HS was not a bad game, it just was not a good one either, repetitive combat and meaningless puzzles it was pretty much enter room, kill everything, move on - repeat. I also found the story in HS to be poor.
That being said I would certainly buy both if they were made and it would be great to see HS2 with a much better story and more variety of gameplay.