In a SharePoint 2007 environment we have one site collection in one content database. This content DB is getting large so we would like to split up this site collection/content DB into multiple site collections and content DBs. Is the best way to do this is by using the stsadm export/import commands? (Not using a 3rd party app) Would it be better to create a site collection in a new content db and then just move the subsite to be as subsite of that site collection? I'm worried about breaking links or workflows.
We are also looking at upgrading to 2013. Are there better/more efficient ways to do this in SharePoint 2010 or SharePoint 2013? Would it be better to wait until after the upgrade to move subsites to new site collections?