I don't know too much about the candidates, but Macron sounds worse than Mélenchon to me: a former investment banker who wants to cut corporate and wealth tax and sack public servants.
He's running on a 90s style neoliberal platform in 2017.
Mélenchon by contrast sounds like a wistful Keynesian—he would certainly drive the state further into debt, but at least he wouldn't prolong economic austerity, pretend that the EU / eurozone project can continue operating in its current form, and seems to recognise that economic inequality causes social dysfunction.
I'm sure French OMITT posters have more insight to offer.