new or old?
With motor skill training such as manipulation of an aircraft controls it is usually better to have an instructor who can explain the process from recent experience of having to learning it for themselves.
Most experienced pilots have honed those motor skills to the point that they no longer consciously have to think how to move a flight control to achieve an outcome, they just do it instinctual and automatic. How do you explain to a student how to do something that you have long since relegated to long term memory. This is where you can see the more experienced pilot become frustrated teaching something that they have long since mastered. It becomes difficult to break down into small teaching bites from first steps.
However when the new instructor with low experience comes to teaching non motor skills such as flight nav, weather interpretation, airfield inspection (airborne), airborne decision making, airmanship etc then they really start to struggle with the lack of real experience behind the teaching.
Best choice is a newbie to solo consolidation then an oldie for advanced cross country and navigation.
As for instruction as a stepping stone, I have found that as long as the new instructor can approach the job as a professional and give their best effort then they usually are always better off for the experience.