Always, always go for the sketch ones!
Like @Tanisha said, they hold more ink and considering the prise it's well worth it.
I've only had sketch, and they've lasted me througout 6 years. Still not dead and oh gosh did I make lots of marker illustrations when I was younger.
(I could recommend the Promarker brand as well, if you want lay down flat colouring. They go extremely well with Copic Sketch on top of it <3)
You could start with the Ciao ones if there's colours you know you won't use too often and buy sketch for the colours you will use the most.