10 day vs 7 day training cycles

8 out of 10 would be running 80% vs 4/7 which is 57%. I bet you would make gains there alone.

Yes, running 8 out of 10 days is (in most cases) more effective than running 4 out of 7 days. 83 additional training days per year usually make a difference.

WHOOPS I meant 8 out of 14! Or possibly 9 out of 14 as I think the 10 day cycle would allow that with plenty of recovery. So same or similar ratio.

A 7 day cycle was created due the constraints of the work week. I've decided recently to do a long run every 10 days rather than 7. I would expect that professional runners do not try to have a 7 day cycle.

It really depends. At the level you currently are, anything that gets you out there more frequently will be helpful. It's not a matter of running a 7day or 10day schedule.