British Experimental Rotor Profile 4 blades have very clever profiles that do not just include the tip. The profile alters from about 1/3 chord to the swept tip. Usual aim is to reduce effect of retreating blade stall and choreolis type wake interaction with the following blade. Downside is higher low speed vibration and potential 'cobble stoning'. That's off the top of my head - I'm sure Google will put me straight. BERP4 is planned for the recently acquired Danish Merlin in lieu of the BERP blades currently fitted to Merlin Mk3.
From what I've seen, the Carson blades look much simpler and do not alter the blade camber with chord length; the main difference appears to be the tips.
Would be interested to know a more 'expert' opinion.