Well, you seem pretty new to the whole concept, so I'll try to explain better about the basics (forgive me if I talk too simply, I don't mean to talk down to you, just trying to help).
There's 2 levels of sharpening a knife. Touching up, and reprofiling. When you get a knife from the factory, it will (should) be sharp enough to slice paper without snagging or tearing it, and shave a bald spot on your arm. When the knife is used it'll dull a bit and you won't be able to shave or slice like you used to. Usually, all that's needed is a quick touch-up. On a Sharpmaker you use the 40º angle holes. Very little metal is removed. Eventually though, after many, many touch-ups, enough metal will have been removed that the edge angle is too obtuse to touch up at 40º. At this point it's time for a reprofiling.
Reprofling involves creating an entirely new bevel grind. On the Sharpmaker you use the 30º setting for reprofiling. Reprofiling with the included medium rods can take quite a while, especially with steels like S30V or D2. This is where the diamond rods come in. Or something like the Edge Pro. Or sending it in the factory for them to resharpen it if you don't want to spend the money on such a system or the time to do it yourself.
The 30º and 40º settings on the Sharpmaker work for most any knife for most any user. The Edge Pro gives you much more flexibility if you want it. Reprofiling on an Edge Pro is easier and quicker than using the Sharpmaker, even with the diamond rods. You can do touch ups on the Edge Pro if you use the finest grit stones, but IMO this removes more material than necessary.
Unless you're overly abusive or obsessive, reprofiling is a rare chore. I've owned both my Benchmade 940D2CF and Spyderco Caly 3 ZDP-189 for a few years, carry one of them every day, use them most days, and touch them up probably a couple times a week. And I've only had to reprofile them each once.
A Sharpmaker will tide you over just fine. Make sure you watch the included DVD. The Edge Pro is a good choice when you have more knives or want to start experimenting with different edge bevels.