I am told that HI8 cassette tape could be equal to DVD in quality for archiving, but DV Mini cassette would be of a higher quality than HI8 and would be recommended for long term storage, future editing, making extra copies of the master tape to DVD for family distribution, etc.

Is this true?

I am asking this as I am considering transferring Home movies (8mm FILM) to digital format.
I own a Sony DCR TRV-530.
I also have access to another camcorder by Canon that uses Mini DV tapes.

The first company I used to do a sample transfer of the 8mm film gave me a Mini DV tape as a master copy along with a DVD finished product.
Another company will give me a better price on transferring by eliminating the finished DVD and supplying only the Mini DV tape. Then I can do my own editing later on.
I asked this second company about putting the master transfer on a HI8 tape but I was told it would be inferior to Mini DV tape for editing purposes.

Recommendations?