ADVC 55+TBC or ADVC 300?

[cmt100]

I need to clean up some old Hi8 tapes as my ADVC 55 doesn't like the synchronization on them. But I can't decide whether to stick with the ADVC 55 and get a time base corrector like the TV One Task 1T-TBC or switch over to the ADVC 300. So help needed to make a decision.

My thoughts and questions are:

Option 1 - ADVC 55 + TBC
One more cable connection so possibly more signal degradation?
The TBC only processes the s-video so what happens to the audio?

Option 2 - ADVC 300
Does the 2D 3D y/c work with PAL tapes? there's a note which says "NTSC only" but it's not clear which bit it is referring to
What's the difference between Line TBC and Full frame?
Does the 300 offer additional filters not found on a separate TBC?

I'd really like a guaranteed to work solution as well!