The main differences are sound reproduction and handling.
A dynamic kick drum mic has a more natural and warm sound and is normally designed to be mounted on a stand, which allows it to be used also with various other instruments besides kickdrums.
A boundary kick drum mic uses an electret condenser capsule, giving it a more aggressive, kick-pronounced, sound. Due to its very flat form factor that is designed to lie on the floor it is very easy in use for kickdrums (as it just is placed inside without using a stand) but makes it less flexible for use with other instruments.