It probably comes down to what you prefer at the end of the day. As you say there are so many variables that come into play which can affect the final result - Voltage at powerpoint, Behmor set-up voltage (220,230,240V), Behmor internal cleaning (sensors), type of bean, age of bean, how beans are stored, ambient temperature/humidity, etc, etc. What one person says works for them, another will say doesn't for them. The only way you'll get a definitive answer will be in your own cup.
Behmor use the "Rosetta stone guide" for the time between first snap of first crack to start of second crack of 2:10min for 1/2lb and 3:10min for 1lb. I'd guess that extra 1 min would show up in the development of flavors of each roast. Personally, I settled on doing 1lb lots to avoid having to roast so often. For me, I've never had an issue with reaching second crack before the roast cycle runs through. Others say they do. I use a true 1lb on digital scales set to imperial which is 454gms. I normally use the "B" time setting and hit COOL when I'm happy with the depth of color. The only time I use 1/2lb now is when I'm trying a new bean for the first time.