My balance is not that great, but I don't have vertigo or oscillopsia anymore. If I stand on one leg and close my eyes, I fall over after about 5-10 seconds. Crossing a log over a rushing stream is impossible, too. But in my everyday life at work, I usually don't notice my disequilibrium; I typically only notice it when I'm walking.
Amy, I'm not sure there is any less risk in having your vertigo get worse with surgery vs with radiation. If the tumor is adhered to your vestibular nerve and must be "scraped" off, the nerve may be damaged as much as it would be by getting a hit of radiation. And the risk of damage to the facial nerve is, from what I understand, considerably greater with middle fossa surgery than with radiation.
Your doctor will be able to give you the "odds" of damage to various nerves and function with each type of treatment. I would recommend you get at least a second opinion. I got 6 opinions. When they all recommended radiosurgery (some recommended CK, others GK), I knew I was making the right decision by choosing radiation. Having a bunch of professional opinions will give you a clearer picture of your options and the general consensus about the best treatment for you and will get you past the roughest part of this process -- choosing when, where and how to get treated.