A residence permit gives you the right to live in an issuing country for a long time. A European residence card will guarantee a visa-free entry to all Schengen and EU states. However, you will only be able to live and work in the country that granted you the permit.
A residence card has an expiry date and must be extended. A passport is given for life.
It is much easier and cheaper to get an EU residence by investment than European citizenship by investment. Residence applications are not as stringent as citizenship applications. However, there are exceptions – those applying for a Malta or Cyprus passport don’t have to pass a language test or prove their integration in a local society.