Which is better for me? A 250 Rebel or a 750 Shadow?

I'm 25, 135 lbs. and 5'10". I have no experience on a motorcycle and am planning on gettin one next year used. Of course im goin to take a training course. I'd be using it for my 20 mile one way trip to work and back home, and for joy riding. I was seriously considering getting a Honda Rebel 250, but I'm worried about not having enough power out on the highway most of my drive consists of. It's a 55 mph limit, but people regularly do 65 on it so I don't want to be run over! The next bike I was considering is a Honda Shadow 750, but my concern with it is it being too heavy for me to handle because of my size, not only driving, but in case it falls on me I want to be able to lift it off. I need an expert opinion and advice. It has to be a cruiser. I'm not into the crotch-rocket thing. Once I'm experienced enough I'd like to add my 115 lb wife on the back, too. That's another reason I was worried bout the Rebel being too small. So any advice or recommendations on which to get are very much appreciated. Thanks!