Originally Posted by AnthonyG
Keeping old threads is a must.
I was part of another forum years ago that did the upgrade from vbulletin, it just never felt the same after. Whatever we choose there needs to be a testing period.
Fear not, for the most part you can just back up the database and import it to a the new database.
Granted I did this back with SMF -> XENFORO, there was some breakage, but it retained the posts at the least.