ES10/15 type is not transparent, it adds noise.
- NR is on even when "off",
- AGC is a bit aggressive
- luma can be hot
- IRE on recorders is always off by a %
These are not TBCs, but rather DVD recorders for MA & Pa Kettle to use. People who had a hard time setting the VCR clock. So many things are forced, to prevent returns and complaints ("that thing don't work right!")
It has an unusually strong anti-tearing, but also has crippling due to Macrovision.
Use it when the net effect is better video, but not when it harms.
ES10/15 does nothing for dropped frames, it's not frame timing correction (not frame TBC). It has non-TBC frame sync. The DVK is your weak TBC that handles frame. And DVK also has downsides (it also needed modding and presetting to not be a PITA to use).
However, this all said, ES10/15+DVK is a solid solution, even if downsides to image quality.
This is budget gear, and so you have lots of caveats and considerations. Actual TBCs, higher end VCRs, are the "it just works" options.
That all make sense?