A major question you'll need to answer is how often you'll travel internationally. That may help you determine whether you take the discount and lock into a plan, or buy the 8830 out right.
If you take the discount, the phone will be locked and you'll pay roaming charges. If you purchase it, it can be unlocked and you can buy local SIM cards when you travel abroad, such as this one -
Low-cost Europe cell phones and European SIM cards
Verizon roaming is $4.99/mo. Germany is $1.29/minute, and the rates are going up this summer.. Here's more info -
International Services