I'd second with what Rob said, I would stick with the Miele. Bags for Aerus have gone downhill and I wouldn't be surprised if the Miele bags are actually better than the Platinum bags. But I have yet to see belts break on both of them, some Mieles I went ahead and replaced the belt because it already comes with the brushroll kit.
However though, the Guardian Platinum to me feels more solid than Miele and Aerus has always been known as one of the most reliable vacuums out there. What you could do is whenever the time comes to either replace the Miele or if you're looking for a second vacuum, you could try out the Platinum to see if you like it or not.
