We've seen that Trump cleans Hillary's clock among independents by a more than 2-to-1 margin, while against Cruz she actually holds a modest lead with them.
What about Democrat likely voters in November? Turns out Trump does better than Cruz here as well. Hillary vs Trump:
Hillary vs Cruz:
If Trump is able to beat Hillary by something like 70%-30% among independents and also steal 1-in-7 Democrats from her, his chances in the general look good. Romney split independents 50%-50% with Obama while only managing to get 1-in-11 Democrats to vote for him.
Cruz, in contrast, would need a huge Republican turnout to compensate for performing worse among independents and only as well among Democrats as Romney did when he lost to Obama in 2012.