It sort of depends, is Angron pumped up by daemon juice or is this Pre-Heresy? If its Post-Heresy then obviously Leman will have to fight an uphill battle, a batlle he would likely lose, whereas if its mano a mano without Khorne Steroids the I'm putting my money on Leman Russ. Hooray for Lemony Goodness!
My advice to you is to get married, if you have a good wife you'll be happy; if you get a bad one you'll become a philosopher.
In the grim darkness of the future the economy has even hit daemons, The Changeling is working at White Castle and Skarbrand is giving head in the alley next to Fateweaver's.You ever receive fellatio from a rhyming demon? It's a bad scene man.
Sticking your junk into a fang-filled mouth that breathes fire doesn't strike me as particularly smart.
Which is why that option should be available to any willing to take it.
In fact, there should be fang-faced, firebreathing demons on every streetcorner offering to pay 100 dollars to give BJ's. The gene pool would be vastly better off without anyone incapable of thinking it through.