Trump is personally obnoxious. But as you say, it is difficult to say what his true positions are. One of the things that indicates (besides that he's a liar but all pretty much any politician is) is that he's actually flexible and bends when it seems called for, he can make compromises. Cruz cannot. Cruz will not. And the President has to be willing to work with the other branches of government. Cruz' record shows he's not willing to work with anyone, not even his own party. His own party colleagues have gone out of their way to hamstring him in-session as a result. That might make him an anti-establishment darling but it doesn't make him a good leader and there's no sign he'd be any different when it comes to foreign policy. "Do it my way or screw you" is not a good starting position for international diplomacy.
That said, I didn't make a claim about which one was worse. I said Cruz wasn't an improvement and he's not. I've vote for Bernie over either (and he's not the Dem I'd prefer to be voting for) so it doesn't matter which one is worse in absolute terms because neither passes the floor-threshold in relative terms.