It doesn't sound quite as good as Sound Checker. K & K has a rough edge that seems impossible to get rid of completely. Then again that may be what you want, and besides the difference isn't that huge.From a practical point of view K & K is a better choice than Sound Checker. Two miniature sensors is much easier to place on a small mandolin than one big chunk of wood. It also seems to be a bit louder, something that's always an advantage. The Twin Spot did produce a little bit of hum, but on a mandolin that's not really an issue. You can always filter it away without altering the tone of the instrument.
Btw, K & K Sound also have a special mandolin pickup, but I don't think it would work on this instrument. Seems it's only for American style archtop mandos.