I started using Mac a couple years ago and I never had slowing down, or virus problems. I have no idea if this is correct but someone told me that Virus makers plan them for PC for whatever reason and not really for Mac, I don't know the logistics but I've never had a virus problem.
If you do have any warranty problems etc, it's so easy to fix because you just book a online appointment and they fix it right there on the spot or give you a new one - that's probably what I like best in terms of piece of mind. And you can also sign up for free lessons on how to use the Mac and make use of its programs etc. Very good for beginners owning one.
They are a bit more expensive but 100% worth it and since the quality is good you can find awesome deals on Kijiji on mint condition ones still under warranty and have piece of mind.