Hi Graham
I had a KLX450 which I used to ride on the sand dunes in the desert around Dubai. The Kawasaki and its big 4 stroke engine suited that riding just fine, the soft sand sucked so much power from the bike.
I sold the Kawasaki before moving back to Europe. Now back in France, I bought my GasGas EC300. I ride on a mixture of fast tracks, dense woodland and slow rocky sections.
Out of the 2 bikes I'm glad I'm riding the EC300 now, it feels light and nimble but still has plenty of torque/power.
I'm not the smallest of riders, 6 feet 95kg.
I used to enjoy riding the KLX450 on fast open desert but it always felt a bit bulky/heavy.
The EC300 is a great bike, just make sure you get the carb jetting set nicely, it will transform the bike. Maybe you'll be lucky and somebody has already done it for you.
All the best, Dave.