For estate- and gift-tax purposes, an ideal valuation is one that's as low as possible, to minimize tax liabilities. Expect the appraiser to look for any documentable factor that might lower your company's value.
For sale purposes, well-prepared sellers equip themselves with a valuation that documents the highest possible value.
For financing purposes, bankers will look for a valuation that focuses on liquidation value rather than a company's prospects as a going concern.
For litigation purposes, valuations are a dog-eat-dog business. Set your valuation goals according to the side of the case you're on, but remember that the best investment you can make is a comprehensive, fully defensible document from the most blue-chip appraiser you can afford.