Question about Microsoft Surface Pro 4, 256GB SSD

The main difference of the i7 version is the stronger, integrated graphics unit and the slightly larger L3 cache. When working in the office, surfing the internet, watching videos, etc.... you certainly won't notice any difference. More complex calculations such as rendering 2D/3D scenes, games and programming work (large scripts, compiling, etc.) will perform noticeably better on the i7.

For normal office applications, the normal Surface 3 is enough.
For complex rendering or drawing programmes, I would use a more powerful processor. But the RAM plays an almost bigger role here.
In that case, I would rather spend more money so that the programmes run smoothly and crash less quickly when processing large data sets. (But that would be really high data volumes)