I've got both a 6800 (53/59) and an SiSl (52/36) and they're both very good chainsets.
I have a Power2Max power meter on the SiSl's, before that I had an SRM - I've also got some normal spiders which allow me to swap between 110bcd and 130bcd.
If you don't need the flexibility I'd stick to the 6800 though- it's a great crankset.
Personally I would not put an FSA crankset on my bike.
I've got both a 6800 (53/59) and an SiSl (52/36) and they're both very good chainsets.
I have a Power2Max power meter on the SiSl's, before that I had an SRM - I've also got some normal spiders which allow me to swap between 110bcd and 130bcd.
If you don't need the flexibility I'd stick to the 6800 though- it's a great crankset.
Personally I would not put an FSA crankset on my bike.