CBR250's are more for the young guy who's trying to convince his parents he needs a 600rr. But instead gets a 250 because it is cheaper, and pleases his parents because it's cheaper and not as fast, still looks like a big boy bike though. The Grom was made for the college students who considered a 50cc or so scooter but wants to ride some smaller highways, (also for the older guys who want something to play around and act stupid on

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I wouldn't give the Grom to a first time rider, it's too small and gets lost in traffic. Takes considerable thinking to remind yourself that no one is paying any attention to you. First time riders need something big enough to be noticed. I always drive like i'm invisible, something alot of new riders take for granite.
The CBR300 is a better U.S bike, IMO, because the 250r looks like the VFR. A bike that many customers don't no anything about or that it even exists. The CBR look will drag more first time buyers towards it, because it looks like big bros 600rr/1000rr.
I honestly think Honda is trying to kill the chinese competition by making so many different models for less money.