My completely science-free analysis (it seems to me) that the less force your fingers have to exert, the less strain you're putting on the internal body parts that actually make that happen. Most laptop keyboards require less force and have less travel, both of which seem advantageous.

This of course assumes that all else is equal (good ergonomic fit, sitting properly, etc. I am not a doctor or ergo councilor, so your mileage may vary.