I am a member of 3 different ones. I'm on my 2nd month on all three. I am giving them all a chance to see which one I like and then cancel the rest.
Zodist: Has "higher end" juice, but is the most expensive of the subscription services out there. I must admit that their customer service as well as their juice has been very good thus far. I have had several email exchanges between some of their staff, and they are always willing to help as well as being very friendly and personal. I don't think I've had any of their juices that they sent that I truly didn't like. I have gotten two boxes from them thus far, and both of them had juice that I vaped completely. Their flavor profile matching tends to follow my personal tastes really well.
Drip Club: Has an interesting 'point' system that allows you to gather points for every dollar you spend with them. You can use those points towards discounts and purchases on their storefront. They also have their own juice shop, so you can buy things that you get in their sample boxes that you enjoyed. Juice is hit or miss with them. I've gotten some really great juice, and others that I have simply given away because I couldn't stand them. I find it is about 70/30 (love / hate) with the juices for me personally.
Easy Vape Club: They have a different system that allows you to choose a specific brand / flavor to send to you every month instead of everything being completely random. So if you get a really amazing juice you KNOW you buy often, you can set your subscription to have them send you that juice every month. You can also select 'random x flavor' for every bottle. They also have a storefront that you can buy juices from them directly. The juice they have sent me thus far doesn't really fit my flavor profile well. Their only choices for random are basically 'random x flavor' so you choose 'random fruit flavor'. There isn't a lot of customization here, so I find that more of the juice unusable for my personal tastes.
My general thoughts for these is that you really must love experimentation and getting various flavors for you to enjoy any of these 'sample' box subscription services. You get some decent price per ml value, but keep in mind you will get juice that you REALLY don't like. If you are new to vapeing, and want to try out a bunch of different things to find that 'ADV', then it may be good for you, but if you have been vapeing for a while and know your general flavor profile of stuff you enjoy, it may not be a good choice.
Hope that helps with your decision.