"What is the best product?"
There are many, many options available for vaping. Personally, I would recommend trying a vape brand that has clear, thorough test results, verified by an established testing lab, included on the package. A strain-specific variety (rather than some of the generic/franken-strain combos) is also good, as you will be able to have a clearer sense of the effects of that particular strain. Leafly.com is a great source for information on various strains and their effects. That way, you can determine ahead of time if you're looking for a more energetic/focused effect, or if you are seeking relaxation/pain relief/combatting insomnia/etc. Every strain is different! I would also recommend using a vape with high-quality glass and/or steel components, rather than some of the cheaper plastic cartridges.