I do not own either, but have used both several times... The Miele uprights are really good. They are solid, quiet and easy to use with the pull and go retractable wand that features a 12 foot hose I believe. You can also adjust the suction, which most uprights do not have that feature. It can be a little heavy if you are lugging it up several stairs or are smaller person. The Riccar is a quality vacuum as well, lesser known (marketed) and has strong brush roll agitation which picks up very well. It does not swivel like the Miele and you cannot adjust the suction. Also the hose and wand is not as convenient/refined as the Miele and its way louder. I believe the Riccar Vibrance is a tad lighter in weight though. If the weight is a concern, you might want to consider the Riccar or even better- the Sebo Felix! Reliability wise, the Miele is a good bet and the Riccar is decent, but have seen reviews and heard of motor burn out a common problem around five years of use or the tools dial on the back breaking/ loosening up. Overall I would recommend the Miele, Sebo then Riccar in that order.
I own a Aerus Guardian Upright, nice machine, but cumbersome with the separate attachments. I don't think its worth the price to recommend it, the above are better options. Good luck