I find it hard to get my hands on large quantities of 70vg/30pg at 6 mg/ml nic. So I mix VG, PG and 70/30 nic of 20 mg/ml. Enables me to go to 7mg/ml or 3mg/ml when I want. Thats the advantage: flexibility.
I might switch to 50/50 20mg/ml nic because I think you have even more flexibility because it’s 50/50