I say the Wolf Rider unit. The extra 'drop' is a very big deal, for one. Second, under 8th edition, I just don't see the practical use of a lone hero on a Wolf. A unit of Hobgoblin wolf riders are slightly more points, but have more wounds and more bow shots. Don't get me wrong...I think lone characters can be effective but they need a little punch & defense (a goblin big boss on gigantic spider, 3 wounds, 2+ armour save, 6 S4 attacks, poison attacks, stomp has a lot of uses). A 2 Wound Khan with a 4+ armour save just dies.
I've fought against Chaos Dwarf armies with multiple Khans on Wolves and merely ignore them (shrug) and if they got in my way killed them (shrug).