My DH has used a Flowbee for years. We bought one off of the Flowbee informercial when they first came out. We started doing this mainly because DH's hair grows so fast, and because of his work, it was so hard to get an appointment for a hair cut. I think we paid about $120, but the prices have come down a lot. (They were very spendy when they first came out.) Between using it for DS and DH, we have saved mega bucks over the years!
A lot of people have made fun of us for using the Flowbee - you know, hooking it up to a vacuum cleaner and sucking your hair. I really can't tell the difference between the Flowbee cut and a hairdresser's cut, once you've used a razor to trim up the bottom. And it's so convenient because DH can do his own haircut whenever it suits him. We are still using the same Flowbee, and have only had to buy one small replacement part over the years. It is quite loud, between the Flowbee motor and the vacuum cleaner noises, but once you get the hang of it, it does not take long to do the haircut. And, it's true, you do not get any hair on you because it's all sucked up into the vacuum cleaner.
I am not familiar with the Robocut, but I can definitely recommend the Flowbee. I'm sure they have made improvements to it since we bought ours. To be truthful, DD and I both have long hair, and I have never been brave enough to try it on our long hair, but it does work terrifically on short hair.
I think I have seen the Flowbee at Walmart or Target. I know I have seen it in one of the B&M stores like that.