Welcome to the club, and sorry you had to join! One of the hard things about these tumors is that there are choices, and no choice is ever perfect. The kind of percentages that you seek should be available from your doctors. Is your tumor 3x5 cm? If so, then I don't necessarily know that that falls into the small category, but I'm not sure. Age is also a big factor in decision making. My understanding is that it is difficult to predict how and how much the tumors will grow, if at all.
The advice here can be helpful, but it is mostly anecdotal. For the percentages of people in a similar situation to yours, I would rely on your professional doctors and/or surgeon. The good thing about these tumors is that they grow slowly, so its not an emergency, and you have time to make a decision.