I'll entertain this. It really depends on ballot access. I would think that Sanders would seem to be a more formidable opponent to Hillary than Trump to Cruz, because Sanders could just use the Green Party's ballots:
http://www.gp.org/ballotaccess, compared to Trump's ballot options:
https://uselectionatlas.org/FORUM/index.php?topic=232226.0, which would result in a really weird electoral map. Obviously, it goes to the House. I didn't really want to spend a long time analyzing this, so there's a little bit of hyperbole, but here it is:
Hillary Clinton/Julian Castro - 228 EV
Rafael Cruz/John Kasich - 244 EVBernie Sanders/Marissa Johnson - 31 EV
Donald Trump/Ann Coulter - 35 EVTrump is basically the George "the South will rise again!!" Wallace 2k16 candidate, except WV which just has a huge crush on Trump. He has a write-in campaign that does very well. Cruz offends a lot of people with his face during his run, but he isn't that bad, so he still gets out the Romney vote and campaigns heavily in FL, while Kasich is sent to MI. Sanders gets the endorsement of BLM, which allows for him to crack 15% in MD and other states which almost gives CA to Cruz. Hillary is kind of just there, but spends too much time pandering to Hispanics. It goes to the House, and Rafael is elected Prez.
Closest states:
FL
MI
WI
IA
CO