Agree with Ben-Anderson: The hell told you that? Yes, it has its limits, but, like any professional or aspiring prof., you are always going to use more than one program to get top quality desired results. Can't rely on one program to get the job whole job done all the time. You can actually achieve your example given IN Sketchbook. It's how you use the tools around/given to you. ie. I mainly work in Sketchbook myself when working on illustrations or concept art, and then expand beyond its limits and go too photohshop for additional effects and brushes.
Download a photoshop demo. Play with it. Some of us who used to draw in photoshop found a breath of fresh air with sketchbook pro. Having more features isn't always better. Having the features you need does. If you try photoshop and don't find anything missing, it may be a better fit for you. I do all my drawing in sketchbook pro now myself, and find photoshop to be terribly limited in what I'm looking for.
Well, honestly - it all depends on what's in your wallet. I'm speaking as a civilian artist, though, not a professional one.
*With Photoshop, you have to sell your kidneys to get it, while Sketchbook Pro is not even over $60.
* Although Photoshop has more tricks and doo-dads, it's more difficult to navigate. Sure, Sketchbook Pro doesn't have nearly the amount of tools Photoshop does, but necessity is the mother of invention. That means that the more limits you have, the better the opportunity your imagination has to stretch itself.
*You can make your own brushes with Sketchbook Pro. And, if you figure it out somehow, you'll be able to convert Photoshop brushes to ones that are compatible with your program.
heres is my experience even with the bamboo tablet. drawing for all programs are easier with this tableti will answer any questions on that if you have any. ok you can get that quality with any program as long as you know how to use them. for example i only understood the layer process and digital coloring from endlessly watching how to or speedpaint youtube videos. type in coloring or drawing in sketchbook pro on youtube and you can see what i mean. personally i hate drawing with photsoshop i mean some do it but i personally hate it because sketchbook idk has more flow or is much more smoother like your drawing with a real pencil. come look at my gallery and all those were drawn in sketchbook. now as far a coloring actually sketchbook is one of the most simpler programs almost as simple as paint to understand. i personally use paint tool sai because i like some tools in it but hey to each his own try all the programs out and see what you like to do best. i colored my avatar with sketchbook pro. if you dont want to spend the loot go to piratebay.org to download it but get the one where you see a higher number under the option SE. because that download was seeded the most. you will need something like u torrent to or frostwire or just a torrent program to download it its not difficult i can help you with that too. just google it