What ever happens the UK will get a bad deal, its merely a question of how bad and how good we can keep relations with our European neighbors. The EU holds all the negotiating power. However, Corbyn has a much better chance of slightly improving the deal and not turning things sour. May will be an absolute disaster, even given the fact she wont tractably be negotiating herself, but will be making the process much harder for our negotiations and will be straining foreign relations. Playing hardball never, ever works in negotiating, you set up the opposition to be extremely aggressive and less likely to compromise. We need the EU to compromise as much as possible so things turn out quite as terrible for the UK.
We'll take no deal.