Kelly is the safe pick. Kobach would be the more outside the Establishment pick who would be attacked regardless of whether he is the DHS Secretary or the Deputy. Both slots require Congressional approval. Kobach will be in the Dem controlled media spotlight regardless. Kris has been the brains behind the immigration movement for more than a decade.
Kelly has already been confirmed by the Senate during his military service. Spot on about it being the safe pick.
Make Kobach the head of ICE