I have never used a dyson, but my mother has had an Oreck for many years. It stopped picking up as well after about 6 years or so so she took it to be repaired and they replaced the motor and did a "complete overhaul" on it for around a hundred dollars (at least 6 years ago) but after that, it ran better than new. She's not had anymore problems with it since. So, she had a new Oreck for at least 6 years, had it "overhauled" and has used it for another 6+ years with no problems. For a $200 vacuum plus $100 in repairs, I think that was a pretty good deal. And as of right now, it will suck up a cheerio from about 3 inches away. :-) Now, she's never had pets so I have no idea about how it does with pet fur, but for general cleaning, it works great.
Now, to give you another side to it, I bought a used Oreck off of Ebay for really cheap and it has never had very good suction. I paid about $80 to have it tuned up and a new roller put on about 3 years ago and it still didn't perform like my mom's did. I haven't looked into having the motor replaced or anything like that because when I really need to get another one, I'll probably just buy new so I can get the warranty with it, especially since they now sell them at Costco. But because of my mom's experience, I would go with Oreck myself.
Blessings,
N.