If you really get the Lansky system for *less* than the Sharpmaker, then go for it (this comes from an owner and user of both).
And if the Sharpmaker is the *old* (pre-204) model with only one sharpening angle, then... (I'd like to say, "forget it", but don't dare just now). You may have to buy additional "stones" for a basic Lansky system later, but that's OK. The pre-204 Sharpmaker is an old model, whose stones won't fit in the new two-angle 204 (for additional information, see the Spyderco forum). The Lansky system is not perfect (some threads on this, too), but it has served me (and my well over half a hundred knives) well for at least three years (I've had the Spyderco system for maybe three years, but used it mostly for touch-ups).
Of the Gatco system I have no first-hand experiences (I'm anticipating a bit here, sorry). The Lansky system has functioned better for me than the DMT system.