We have both. The M6000 is a little easier to ride. It is the same chassis with some weight off from the M8000, The power is great for a 600. It is really good on oil and gas!
It Depends how you ride. And what you expect from the sled.
If you would be happy with a powerful 600 this is your sled.
It is the perfect sled for my wife who has been riding since 2005 and weighs 125 with gear. this sled is making her a better more confident rider.
She loves it.
I have only ridden the machine maybe 20 mi. but it works good. I am guessing the power is close to my 07 M8. I think for me it is fun but I want more power (but then I want to big bore my 800)
If a 600 will do it I don't think you would be unhappy