I've had to go to different suppliers depending on my needs at the time. At first I liked it pre-mixed for me( 70PG-30VG) right at the level I vape at ( 12mg/ml). That really narrows down suppliers. Some Only sell 100mg/ml.
I still, after a few years, only buy 24mg/ml and mix it down. Just a years worth-1 liter. I still find I only trust a small handfull for the best and most consistent.