Well i think if you are doing networking and you really want to be very good at it, then you should use windows so the apple laptop that your teacher wants you to buy i don't see why you should. For networking guys, you will mostly be dealing with systems on the windows operating system. Apple is not widely used in Ghana so it will not be wise in terms of business. Again even though apple laptop looks sleek and all, it is over priced and not anything special. When it comes to computers, you need two things, Power and control.
Apple laptops are locked most of the time. People who are new to computing find it difficult to use. If the laptop should be become faulty, it is very expensive to get it fixed. To an African, Apple devices are just status symbols, they are nothing special though.
if you really really want to harness the power of The computer, you should buy a computer that you can easily hack yourself both hardware and software wise. If you want to learn how to use the mac, learn unix instead or better still go with the linux philosophy.
So in summary, buy a laptop that is not apple but have either i5 or i7 processor, with at least 500gb hard disk space and at least 2gb ram. Asus is a good laptop and i like their sleek and flat design so you can buy that one. You can buy any laptop so far is it has the qualities i described above. The reason why the laptop should come with windows is that as a beginner learning networking, you need to know your way around the windows system, be able to hack it, break it, destroy it and fix it. When you conquer windows then you can join us in linux heaven by installing any of the linux distros, preferably backtrack linux. Installing linux or unix is far easier and better on a windows machine.
To be a real computer master, you must be able to make both the hardware and software of any computing architecture your bitch starting with windows. ONLY AFTER ACCOMPLISHING THIS SHALL WE CALL YOU MASTER.