U-locks are strong but also heavy and so are inconvenient while travelling. You can have a frame mount for that. On the other hand, you can just wrap the cable locks around handlebars, and that is it. In theft deterrence, both the lock types cannot be easily cut with a basic bolt cutter, grinders, or any other cutter. But only when you choose to buy a good quality product. So, the bottom line is both lock types has pros and cons. If you want something portable, you can go for cable locks and otherwise, U-locks can be your choice.