What would be the time difference on i5 and i7?
2.6 i7= 12,800
2.3 i7= 11,700
2.5 i5= 7,200
It is going to be slightly more complex than this, but unless someone on here has both an i5 and a i7 mini and encoded the same video with both using Geekbench will give us a rough idea.
2.6 i7 is ~78% faster than 2.5 i5 and 2.3 i7 is about 63% faster than 2.5 i5. Should give you a rough estimated of how much quicker a project will be on the i7.