The main disadvantage of the official dock/desktop cradle for the HTC EVO 3D is that it can only be used with a bare phone.
The new Seidio dock, on the other hand, includes a removable plate that accommodates most of the company's cases and extended batteries. Other third-party cases would most likely fit into the dock as well, though for obvious reasons Seidio cites compatibility with only its SURFACE, SURFACE with kickstand, SURFACE Extended, ACTIVE, and ACTIVE Extended cases. The Extended cases are the ones that work with those massive 3400mAh and 4000mAh Innocell batteries. Please note that the CONVERT case is not supported.
The dock is designed for charging and syncing (rather than outputting video to a HDTV) and will automatically launch dock mode when the phone is properly seated.
This dock is chunkier and less functional than the official HTC cradle, and its price reflects that. There are two versions available: the Desktop Charging Cradle for $29.95 (includes dock and microUSB cable) and the Desktop Charging Cradle Kit for $39.95 (includes dock, microUSB cable, and travel charger).