Between the two, there is a
16% performance difference. There is also a 15% price difference (looking at Newegg).
One thing that you have to consider is that you're not comparing the same product level. You're comparing the top Haswell i5 to the mid range Ivy i5.
Now it's up to you whether you want to pay abit more and get abit better speeds, along with future proofing (assuming Intel uses the LGA 1150 socket again), or pay abit less, and get abit less performance.
Personally, I would go with Haswell, as it's the newer architecture, along with it being more future proof. Also, the low power capabilities of Haswell can be useful if you live somewhere where electricity is expensive.