A 1-48 is a versatile twist, it will do all kinds of projectiles, I have shot PRB sabot and conical with good enough accuracy for hunting. Of course any thing that is made to be versatile is not going to be the very best in all situations. It is good enough to be what most people like the best. Part of the difference is if you us some of the old methods for determining how much powder you want, to me using the guns my grandfather or I made a charge of 130 gr was not unusual in commercially made guns you should go by what the manufacturer puts in the manual as the material is not always of the very best quality, and the parts are not hand fitted and have "tolerances".
Also people that have not made there own from scratch and proof tested them have a different scale of what a heavy or light charge is, ton me a charge under 90 gr is a light charge and a charge over 120 is a heavy charge. The point of max efficiency changes with different powders and with the different bullet weights, very few of us a looking for the most efficient powder load, the load of max efficiency is never the highest velocity but is the point at which you get the most feet per second per grain of powder. Due to age how long we have been in the sport and past experience we tend to use different terms while meaning the same thing. I have noticed my self and mike do this every once in a while. Lee