Plug
Obviously the choice of plug of your vacuum cleaner is probably not high on your list, however it is important that like the power cord it is rated for the amount of power your motor draws. It should also be fused with an appropriate rating of fuse.
The range of plugs available is far more restricted than the range of cords because of the strict safety rules around plug design in the UK. In other countries there may be more variety, however I choose a simple heavy duty 13 amp black plug for the Mark I vacuum cleaner, and a orange version for the Mark II vacuum cleaner.