See here (2nd part huge list of owners reports)
http://www.visordown.com/forums/showthread.php?t=266079
and here for a load of bikes for sale
http://www.visordown.com/forums/showthread.php?t=174562
And my own little summary from a thread on VD to the very question you asked
"Hi Mate
The short answer is how long is a piece of string
Unfortunately for you this subject comes up quite a lot so you might not get a great response and most peoples opinions are based on their own bikes, so don’t expect a clear cut answer. You best bet is to check the which supermoto sticky and read the reviews of all the different bikes.
From my experience motards are either street bikes or race bikes and although both can handle the other the street tards ain’t gonna be as good on track and the race bikes are gonna be mental but will need looking after. Its up to you to decide what you want and how much effort you want to put into looking after the bike.
Heres a rough guide to whats what, but there is no subsitute for getting a decent test ride and making your own mind up.
Street tards usually have decent service intervals (1500-4000 miles depending on bike) weigh about 135kg-150kg and put out 40-50 bhp as standard. I have listed some below.
KTM LC4
KTM Duke II
KTM 625/660SMC
CCM R30
CCM 644
Yamaha XT660
Suzuki DRZ 400
MZ Mastif/Baggy
Husky 610/510/450
etc
Race bikes are gonna be lighter and quicker but as i said they need looking after, service intervals are anywhere from a few hours to 100-600 miles, but they will weight 100-130kg and so be better handing. Again I have listed some.
Honda CRF450
Yam YZ/WR450
KTM 450/520/525
Husaberg 450/501/550/650
etc
The most popular street tard on this forum is the KTM LC4/625/660SMC’s which are great do it all motards this doesn’t means its the best, but they are popular for a reason. I ran 2 KTM’s over 4 years and put 13,000 trouble free miles on them and loved every minute
But some people don’t like the vibes, or prefer other makes so as i said try and get a test ride if you can. Its your cash.
IMHO I would go for a KTM 625SMC or a Husky 510. But thats my very biased opinion
"