To answer your question about durability, though, the Studios are more durable than the Solos but I have heard of the headband snapping on occasion. The cables are supposed to be fairly durable--I haven't heard anything about cords snapping but I have heard of them wearing out. Replacements aren't cheap, either.
Sennheiser and Grado are coveted amongst audiophiles, but having a decent audio source is important, and your own preferences will affect your perception of how good they are for you, personally. Either way, with Beats you are paying for the name and the stylish design when you can get better quality for less. You can definitely get better for what you're willing to spend.
This site offers a lot of information on good headphones based on what features you want: