The i5 is probably better.
Cores/Threads wise, both processors are the same, with 2 cores 4 threads with Hyperthreading.
But the i5 has an overall higher Clock Speed (Including the Maximum Turbo Speed), and has Turbo Boost technology, allowing it to turbo to 3.5GHz from 2.7GHz. although the i3 runs at 3.3GHz maximum, and doesn't have turbo.