Well, from my understanding, a sintered base is a higher quality base that performs a bit smoother/faster,etc., but also requires more waxing/maintenance. An extruded base will require less waxing and is much easier to repair and maintain.
This is correct. I'm not 100% sure on the semantics of them necessarily being higher quality, but sintered is more expensive, requires more maintenance, and will be faster than extruded if kept up. Extruded will be faster than a poorly kept sintered base, so if you want less work go extruded. If you're OK with keeping your base up, go sintered.