I ride a 99 yz250, and I love that bike. I grew up racing mx and now I mosty ride trails, grass tracks, and a little mx and that bike suits me really well. It has plenty of punch to push me over any triple and up any step up, and it is very controlled in the trails with the right clutch/throttle control. Out of the Japanese bikes the later model yamaha's are the best all around bikes because they are the only company still putting research and developement into their 2 stroke programs. Other than that, KTM builds great smokers, but they can be a little more pricey and more difficult to get parts for. The great thing about my yz is that I can get all kinds of aftermarket parts or oem parts at the drop of a hat at a very inexpensive price.
About the power, I know you rode a big cc smoker before, but that bike was built in the days before power valves, better heads, and piston upgrades. You would be suprised with what a 2 stroke 250 puts out now and it would probably outrun your old Maico, and it has the benifit of much better suspension and it's MUCH lighter.