I have both. I prefer the sharpmaker, but the lansky is better for reprofiling edges. Although the sharpmaker is no slouch with the diamond rods, it takes longer. Less fiddly though.
If you could only have one? Sharpmaker.
Spyderco : Resilience, Tenacious, Persistence, Manix 2 G10, Manix 2 LW, Para 3 G10, Para 3 LW, Paramilitary 2, Sage 5, Amalgam
Kershaw : Tone, Cryo, Cryo 2, Thermite, Atmos, Natrix 7007cf, Natrix 7008cf, Bareknuckle 7777, Concierge
Zero Tolerance : 0566CF, 0770CF, 0770GRYBW, 0562CF, 0470
Ontario : Rat 1
CRKT : Caligo
Civivi : Plethiros, Baklash
Cold Steel : AD10