Hi and be welcome here brakmaren,
if you ask me, I would prefer a 98 501.
In my opinion, I have made my own experiences with a 99 Husa,
the 98 had a bit less problems than the 99. I think you don´t
need the PDS damper, the old Husaberg rear suspension worked really
very good. Maybe, when you have some luck, you get a bike with Oehlins damper.
The engine got some changes in 99 and in first step it weren´t not the best changes for the engine. The engine got stronger valve springs but the valve seats were too weak. So many people had problems with their valves/valve clearance etc. I was one of them.
My first Husaberg was a 99 and not only because of the fact that is was a 99 model, but of less or none maintenance of the guy who had this bike formerly I had a very bad engine damage after 3 months of riding.
With the new ignition the bike theoretically runs a bit smoother and the rider should give more controlled power to the ground. It works quite good, but if you have a damaged ignition (stator) you won´t find one on the used spareparts market. The older ignitions were the same as you find at the KTM LC4. So its easier to find one of them. I think it´s an advantage.
If you´re thinking of buying one of these models I would recommend the 98 model. I think it´s a bit cheaper. You can also buy a 97, it´s nearly the same bike as the 98. Or you buy a 2000. But with the new design it will cost a bit more. 2000 they had nearly no probs.
I would also recommend a 501, because a bigger bike with 600ccm makes fun, no question, but riding off road, and maybe MX will become a fight with the bike after a few laps. Too much power that you have to get under control.
So, hope I could help you,
not that easy in english
greetings
hribman