Yes should have mentioned what system I was coming from...
It is a Xinet Webnative Venture db and its really badly configured so I can't use folder structure. And to answer your other question I'm pretty confident in both CSV and XML.
This is how I think I'm going to do it:
1) StaticSync to ingest the assets. This I will do 2nd level folder at a time.
2) Once the assets are in I will export the meta data from the ingested assets into CSV.
3) I will then merge the ingested asset data with the meta-data exported from Xinet
4) Do a CSV Upload to update the meta-data of the ingested assets.
I think this should work. I'm currently doing a test staticSync on a good sized test folder of about 50gb. That should give me a meaningful test.
However if anyone knows a slicker way of doing this I'd be happy to hear.