Advantages and inconveniences

Hello everyone,

I'm new on this forum but i've got a little experience on Drupal. I apologize for the mistakes on the syntax or on the words because i'm french ans i'm not an expert in english.
I would like to know somethings about drupal, more precisely about Multisite/monosite and Multibase/monobase.

Can you tell me the advantages and inconveniences of a drupal installation monosite, a drupal installation multisite, a drupal installation monobase and a drupal installation multibase.

Cause i've ever think about that i tell you what i think:
_Monosite:
_advantages: no one.
_inconveniences: you are obligated to make a second installation of drupal if you want another site.

_Multisite:
_advantages: Only one installation of drupal, make several site easily. Modules and themes can be share or they can be for a unique site.
_inconveniences: no one.

_monobase:
_advantages: If the base crash you just have to do one backup. I think that the maintenance is easy.
_inconveniences: Maybe the charge?

_multibase:
_advantages: Maybe the charge?
_inconveniences: If the bases crash you have to do many backups and the maintenance is more difficult. (I'm not sure)

Thanks for reading, i'm waiting for your answers.
Have a good day.