It highly depends on the use case. If you can live without x86 desktop apps, which for the typical tablet user is most certainly the case, the surface 2 is in almost all instances the better choice. It is lighter, thinner, has only passive cooling and lasts longer.
Even from a gamers perspective the surface 2 can handle the touch optimized games in the store well. If we are talking desktop games, the surface pro 2 would only be a compromise, since any ultrabook with discrete graphics is better.
I guess that is the reason, that in between my ultrabook and my Surface 2 there is no space for a Surface Pro 2 since the Pro 2 is a bad compromise as tablet and a bad compromise as Ultrabook. It can replace neither very well.