Deltas use too much space for less printing area, i dont like this. Anyway, prusas and grabers are a good place to start printing, but not to use it professionally. since they construction and structure is not so realiable for a 100h+ printing.
About the autoleveling, try replacing the tool (endstop, inductive sensor, whatever makes it work). the autoleveling feature should have a precision of at least 0.005mm, thats waay more than our hands/eyes can do.