It's largely a matter of personal preference, except that jmol can be used inside a browser. I actually use DeepView (https://spdbv.vital-it.ch/), but largely because I am used to it and know how to quickly get the results I need. Development activity with both jmol and rasmol are higher, both are open source.
Depends on what you want to use it for. Jmol has a richer command set beyond the basic protein display commands, e.g. Molecular orbitals for small molecules, specific display options for inorganic crystal lattices, user defined objects.
Compare: http://www.openrasmol.org/doc/ to https://chemapps.stolaf.edu/jmol/docs/ . If it is just a molecular viewer you want, PyMOL is a third option, particularly if you need to produce publication-quality images. If you plan to do any molecular modeling, Deep View and Chimera https://www.cgl.ucsf.edu/chimera/ are good free options.