Each of the programs listed are geared toward very early-stage companies and provide many different types of support functions. Each program (I believe) offers grants or loans, office space, and mentorship. At its current state, the Techarb is more of a conventional incubator with outside entities providing financial and mentorship functions, however it is intended to be grown into a full accelerator in the near future by U-M (it was created only a few months ago and just getting off the ground). I'm less familiar with the SmartStart's program (I only visited once), however I believe it offers a full range of early-stage startup assistance.