I prefer to start on live mice because it allows me to get 98% of my hatchling eating their first meal first time offered with live rats that percentage is lower.
After 3 meals at switch to rats, as for F/T more often than not it's on request for people with payment plan (usually take several weeks to completely switch an animal), and I might switch some here and there to help with sells.
In general I feed live obviously with 100 to 200 hatchlings to feed it makes it a lot easier for me.