Is it big difference between Mac and PC user for Sketchup?
Completely depends on your use case.
Depending on how large the models you work with are and if you are rendering, but the short answer is yes. The more computing power you put in the bigger the performance reward.
If you have a MacBook Air already then the best way is just to download the free SketchUp make 2017 client and test it.
There are some GUI differences, particularly in regard to Toolbars/Trays and the Materials editor, but the functional core is all the same. As has been said many times, the biggest difference is that you can get a more powerful PC for less dollars than a Mac - which trades off against your preferences for OS and what other apps you want to run.
Thanks a lot. I have allredy MBair. I will try 2017 version. Is it also for Mac users?
Thanks. I will consider to bying PC for this case.