I have NOT found success testing messages out of context, like in surveys. It’s hard for respondents to truly put themselves in a buyer’s mindset. I’d recommend putting messaging into practice, in context, in ways that you can test and iterate. For example, look at lift in conversion on landing pages, ads, or emails with messaging A vs. messaging B. Put pages up on sites like UserTesting.com to hear first-hand from potential customers (I’ve found a lot of success with the screeners they offer). Ask sales reps whether they’re having success with your materials, and where they’re hitting friction.
As you learn what works, you should feed that back into your understanding of the customer. Did the messaging that flowed from your customer profile resonate best? If not, why not? Reach out to a few more customers or throw some more tests up on UserTesting with specific questions, and continue to iterate from there.