The discovery 2200 is a great machine , I used one for many years and found some great items with it. The 3300 is , from what I can see, a step above. It has a few more options over the 2200. If you can afford it, I think the 3300 would be the way to go between them 2. The pinpoint option on it, over the 2200 is worth the extra money itself. But is not something absolutly needed, all up to the user.
After using the 2200 for years I was going to upgade to the 3300 when I stumble across a great deal on a Garrett Ace 250. Like bounty hunter said ,it is also a great machine and does have pinpoint.
They,3300,ace 250, are in about the same price range or at least not a huge difference. Its really hard to say. I think you would be happy with any one of the 3.
I know that didnt help much,lol. But to answer your question,IMO the 3300 is the way to go.(In your post,you did not ask about the ace) There are so many machines out there, could go on with this forever There is no answer in stone.But out of these 3,,, any one of them will hang with the best.
Good Luck