RealClearPolitics is well-known for their averages of top polls. Go here to see how Trump and Cruz fare versus Clinton in their "poll of polls." Today the site reports Cruz comes out slightly ahead of Clinton, Trump does about 5% worse, losing to Clinton.
Bottom line, today Cruz is the more electable candidate according to the averages of four polls. Much can happen to change these numbers between now and November, or even between now and the convention this summer.
I prefer the cool intellect of Cruz over the bravado and bluster of Trump. I understand my bias in this regard is not widely shared; mass popularity is needed to win the White House. I wouldn't be surprised, for example, if Trump proves more able than Cruz to win over blue-collar white Democrats, much as Reagan did, and for some of the same reasons. Either man is infinitely preferable to Clinton.