Thank you for contacting the Intel Communities.
It would depend in different facts or specs.
i5 processors are very reliable and they would provide you with an excellent performance, i7 processors would be for high end solutions, more intensive processing, and more "juice".
For that reason it would depend on your needs and also the models that you are comparing.
My recommendations would be, check which are your needs, meaning requirements of possible software to be used in the computer and the type of usage, gaming, web browsing, watching videos, graphics design, etc.
Also, in this website, ARK | Your Source for Intel® Product Specifications, you can look for the model of the processors you would like to compare and easily see the different specifications for each.
How to compare the processors?
-Look for the model of the processor "i7-4750" and look for the blue compare button at the right side of the page.
-Look for the second model
-Hit the "Compare Specifications" button at the top of the page.
Do not hesitate to contact us back if you encounter with additional questions or concerns.