Depends on your purpose for using it. Many ground covers are used simply to keep down weeds, keep top soil from blowing away or washing off, to stabilize drainage, prevent water pooling, etc.

But true cover crops are planted with the goal of improving the soil while it is dormant. They are then turned into the soil and allowed to decompose, release nutrients in the process, and improve soil tilth. That is always my goal so I prefer using one of the many legumes like field pea blends.

Cover crop discussions

Dave