N9: Diffrence between flashing with firmware vs restore factory settings?

Hey guys!! Please - I need some help.

What is the difference in the effect of
restoring factory settings vs flashing the device with firmware?

My n9 (already updatet to pr1.2 OTA) is running kinda slow and having a few bugs,
that aparently isnt "normal" bugs.
(for instance I cant:
update facebook/twitter status under availibility
get my google acount for gtalk to work in acounts)


Furthermore I can read in several forums that it's better
to update your device via flash/firmware
instead of OTA or NSU... how can that be?

But I hope that "clearing" the device will help
radically with the speed issue +hopefully repair some of the bugs..

Hope you can help me.

I miss my good old smooth working and fast N9 !!

Thanks in advance!


BTW...Great instructions!!! Maybe I should try this flashing thing.. not THAT big of a computer-geek thoug :-)