Extracts are almost always alcohol-based. Many feel that the high percentage of alcohol make the taste bitter.
You may be concerned that some extracts may also leave deposits on the atomizer over time. Such deposits could lead to a short atomizer lifespan, or may require a more aggressive cleaning regimen. Nothing about this has ever been proved to my knowledge. If it's safe and tastes good,
vape it - atomizers are cheaper than analogs.