The i7-4510 does have a higher turbo boost frequency so it will have more power if you do need to tap it.
One interesting thing about the i5-5200u is that it does say that it can have up to 16 GB of video memory, while the i7-4510's iGPU only can have 2GB of video memory. This may be a moot point if you are getting a laptop with a dedicated GPU.
Since the two processors are similar, the rest of the features of the laptop, price point, form factor, and user reviews will probably be more important in choosing a laptop.