I test rode both the Langster and the Capo. The Langster to me felt like a turd compared to the Capo. The Langster seemed to me like it was built for recreation. The Capo frame is more responsive. Never rode a Sputnik.
Prepare to spend some extra and change things on any fixie you buy is my opinion. I was dissapointed in the fact that the Capo does not come with a fixed gear, only a freewheel. I bought the fixed gear and ring and switched it around right away. Took the freewheel off and am not even sure where it is now. I changed the bars out to a set of TT bars with only a front brake. Also switched to a different seat. the seat that comes on it was not comfortable to me.