Vostok - well, you have to look at believability (if thats a real word). By this, people will not believe that Geonosis is the Confed homeworld, seing as the Republic captures it in Ep2. If it were, there would be no more Clone Wars.
Also, with Kamino and Geonosis, they are both production facilities, not Administrative center's, which is needed for a capital. It's like saying that Detriot should be the capital of the USA.
Given Alderaan's high position within the Republic, and the fact that the destruction of that world would 'make a good example', plus the continued dedication of the Organa's to the Jedi makes it a good Republic capital world - that, and it is actually in the Republic.
Same thing goes for Muunlist.
Dark Lord of the Purists
Inter Arma Enim Silent Leges