The differences far outweigh the similarities, in our opinion. An important in is the cord, on the ST-700 it's connected to both earpieces, instead of going through the headband like on the Beats Solo. The cord is nice and thick, so it won't wear through in the first instance. The flipside is that it's somewhat inflexible, but you get used to it. The standard cord is 60 cm long, a practical length that's long enough but won't get in your way. If you want a longer cord, the included extension cable makes it about 150 cm.
The earpieces can be folded in so they take up less space. Extending and shortening the headband is partially with increments, and partially without. The top of the headband is made out of a type of soft fake leather that contains foam rubber. It feels nice on your head, in any case.
The pressure on the ears is less pleasant, on the other hand. Like many other on-ear headphones, the ST-700 sit very tight. It will of course differ depending on your head and hair, but if you don't like pressure on your ears, these headphones are probably not for you. Each side has an L and R marking, which is good considering the symmetrical design.