Hi all,
After several months of testing, We've just successfully migrated from Vbulletin 3.8 (with latin1 charset & arabic language ) to SMF 2.0.15 (UTF8 charset )
Stats of my forum:
Members: 250,000
Posts : 670,000
Topics: 90,000
To move from dedicated server for the vbulletin forum to VPS server for the SMF forum + reduce the size of database (than reduce the price of the server from 37 $ to 9 $

), I had to empty up some of tables like : customavatar; customprofilepic; picture; sigpic; socialgroupicon; socialgrouppicture; tag; reputation; tagsearch; humanverify; externalcache; visitormessage ; visitormessage_hash
To redirect all my vbulletin forum links to the new of SMF, i used this file .htaccess form
https://www.simplemachines.org/community/index.php?topic=554897.0 with some changes :
RewriteEngine On
RewriteBase /
Redirect /index.htm /smf_forum/
# SMF rewrites for vBulletin after vBSEO removed (including forum directory)
RewriteCond %{QUERY_STRING} ^t=([0-9]+)&page=[0-9]+&p=([0-9]+)#[0-9]+(.*)?/?$ [OR]
RewriteCond %{QUERY_STRING} ^t=([0-9]+)&page=[0-9]+&p=([0-9]+)(.*)?/?$
RewriteRule ^(forum)?/?showthread.php$ /smf_forum/index.php?topic=%1.msg%2#msg%2 [L,R=301]
RewriteCond %{QUERY_STRING} ^t=([0-9]+)&page=[0-9]+(.*)?/?$ [OR]
RewriteCond %{QUERY_STRING} ^t=([0-9]+)(.*)?/?$
RewriteRule ^(forum)?/?showthread.php$ /smf_forum/index.php?topic=%1.0 [L,R=301]
RewriteCond %{QUERY_STRING} ^f=([0-9]+)&page=[0-9]+(.*)?/?$ [OR]
RewriteCond %{QUERY_STRING} ^f=([0-9]+)(.*)?/?$
RewriteRule ^(forum)?/?forumdisplay.php$ /smf_forum/index.php?board=%1.0 [L,R=301]
RewriteCond %{QUERY_STRING} ^do=newthread.f=([0-9]+)(.*)?/?$
RewriteRule ^(forum)?/?newthread.php$ /smf_forum/index.php?board=%1.0 [L,R=301]
# SMF rewrite for cms author
RewriteCond %{QUERY_STRING} ^author/([0-9]+)-.*/?$ [OR]
RewriteCond %{QUERY_STRING} ^r=author/([0-9]+)-.*/?$
RewriteRule ^cms/list.php$ /smf_forum/index.php?action=profile;u=%1? [L,R=301]
# SMF rewrite for calendar
RewriteRule ^calendar\.php /smf_forum/index.php?action=calendar? [L,R=301]
# Rewrite all non-existent directories and folders to /smf_forum/index.php
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ /smf_forum/index.php? [QSD,L,R=301]
Thanks to all.
Good luck to all