are there any bad years to stay away from?
I don't think there is such a thing, since there were so few changes. After '95, I believe the only changes are graphics, and I think I read somewhere that the footpeg attachment is modified slightly after '98 or '99, if I remember right. Certainly nothing significant.
are there any chronic problems that i should look for symptons of?
The only issue that merits discussion is the history of piston skirts cracking/disintegrating on some 220's. Generally this only happens on bikes with aftermarket pipes and that are ridden hard (i.e. up in the rev range). I would not let this stop me from buying an otherwise clean used 220, as you'll likely want to start with a fresh top end anyway.
If the previous owner has left the jetting a bit sloppy, the power valve mechanism can gum up to the extent that the drive gear will strip. This usually becomes apparent by a loss of top end power as the valve never opens. Since you'll probably clean this up when you freshen the top end, it's really not an issue.
what are the pros-cons between the 200 and the 220?
The link Fred gave you is a good summary. I will add that putting a desert (Rev) pipe on the 200 changes the character of the bike considerably. In tight & rocky woods it's more than this Senior C rider is comfortable with, although it's a hoot in open areas. With the woods (Torque) pipe and 13/49 gearing, it's perfect for me. I rarely ever need 1st gear except to bail me out on a hill, it has more top end than I have the nerve to unleash, and I can loft the front end at will at anytime. I only weigh about 150, if I was closer to 180 or more, perhaps the extra grunt of the 220 would be preferred.