I keep flip-flopping on my carto preference from lower (1.7, 1.8) to higher (2.8, 2.9) ohms that I have.
I usually end up at around 3.7 to 3.9 on the lower ones, and on the higher ones, I think I'm usually between 4.4 and 4.7.
It depends a bit on the juice, and also on how that particular carto happens to be wicking...