Interviewing Realtors

Based on limited personal experience, I would only negotiate the commission down if that reduction comes out of the listing agent side. The first house I sold they agreed to cut down the total commission from 6 to 4% each side getting 2 instead of 3%.

After the house sat, I raised the commission back to 6% and added a bonus to the buyer's agent if the house closed within so many days. The house sold almost immediately.

It just seems like you want to distinguish your house in a positive way, if at all.