The blank stare from an associate I was interacting with used to freeze me in my tracks like a deer in the headlights when I was a new shopper. It's still awkward, but I don't let it throw me off my game anymore. I poke and prod to give them the best possible chance of salvaging the situation, but I won't spoon-feed them.
Sales = making the customer believe that a certain product or service is a solution or of benefit to them. With proper training, any associate should be able to know and express the basics of why the customer should make the purchase.
Good questions for you to pose to the sales associate...
"Which would you buy?"
"Which one do you have now?"
"Why do you like the one you have?"
"Why do you think this one is better than the others?"'
"Which one of these is your best seller?"
"What would be the best bang for my buck?" (if on I'm-on-a-budget scenario)
"I want the best, because I don't want to be replacing it anytime soon or wishing I had the latest model." (if on a Got-money-to-blow scenario)
Try to avoid yes/no questions like the plague.
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"Between stimulus and response, there is a space.
In that space is our power to choose our response.
In our response lies our growth and our freedom."
~Viktor Frankl