From an objective pov : Vita because more games coming, good support from first party+third party unlike Wii U with just first party support.
also, Vita sold more per week than Wii U this year and will reach +7M in 3 weeks
Predictions for end of 2014 HW sales:
PS4: 17m XB1: 10m WiiU: 10m Vita: 10m