You will get about as many different answers for about the same number of replies with that loaded question.
For me I would say MBV is very good as far as customer service, prices, and some tasty juice as well. Cinnamon Roll has been a big-time hit for me from MBV. I still have many to try as well.
With that being said, there are many eliquid vendors that produce a great product. Most seem to have an area that they excel at, where they tend to lack in other areas.
So to answer your question better, you would really want to know what you are looking for. For example are you looking for a Tob? If so what type. Do you want the eliquid made in a certain part of the world. How about PG &VG ratios. The list goes on and on. Like I said each vendor seems to have thier niche, and they do it well.
Just remember, to have fun with the quest and look for samples whenever possible. That will save a lot of money for you. For example MBV doen't really offer samples, but their prices are so inexpensive that their 15ml bottles are about the same price for other vendors sample sizes. In that case no harm, no foul. Where as another vendor may charge double the price (or even more) for a 15 ml sample.
Something else that may help is look at the vendors website for customer reviews when deciding on a vendor and/or flavor. Also do some searches within the ECF forum. There has been someone say something about every flavor from every vendor.
I hope this helps you a little.