The category system within deviantArt has the purpose to organize the thousands of artworks submitted every day and group them together in accordance to style, media, genre and/or theme, etc. Imagine deviantArt without categories, it would be a chaos! Imagine yourself wanting to browse for photography only; without the system organizing every deviation by media, you would find yourself unable to filter artworks that aren't photography in your search results.
Thus the importance of categorizing your artwork correctly. By submitting your work to the appropiate category combined with a correct use of keywords, you're a step ahead of being discovered by people wanting to search for art like yours.
All this sounds so nice and all, but what happens when a particular piece could fit in several categories? The category system as it is now is very specialized and has literally thousands of different subcategories buried down tons of more subcategories, which is both a blessing and a curse. Having an specific category for almost every art media, genre, subgenre and theme is great... if you know how to use it. Unfortunately a system this specialized can also be pretty complicated, specially if you're new to the site.
I already gave a very superficial introduction to the different categories within Digital Art, which are mainly organized by media and genre. A Fractal is not the same as a Photomanipulation and that's quite evident so most people don't have a problem categorizing their fractals or photomanipulations... or pixel creations or digital drawings, etc. Today I'll touch a situation in which the category system is a lot more tricky.
Digital Art VS Comics & Cartoons VS Anime & Manga VS Anthro VS ... you get the idea
Maybe you could think that a drawing created in Photoshop should be submitted to Digital Art > Drawings, and reading that without any further context I would also agree. But before you click the Submit button, stop for a moment and think of your drawing. Think if Digital Art is indeed the most appropiate category for it, imagine yourself searching for a drawing like yours, would you search for it in Digital Art? or would you try in Manga & Anime or Anthro or Fanart?
Which category would you submit it to?
If your answer was Digital Art then... you would be right, after all is an artwork created with a digital program.
But if your answer was Manga & Anime then... you would be right also. It's is clearly and heavily influenced by the Manga style.
SO WHAT TO DO THEN??! If both answers are correct then which should you submit it to?
Well, you don't have to choose between the two, this is why the Manga & Anime category has its own digital division, so the most accourate answer lies in:
Which btw also have other subcategories similar to the ones you can find in Digital Art, such as 3D, Vector, Paintings and Drawings. So if you think about it, if you create a Manga piece with digital mediums, there is an specific category for it as opposed to the general Digital Art category.
What's the difference then?
Technically neither of these options are wrong, the example deviation is in fact in the Digital Art gallery and even received a DD, technically is not a miscat. However if your artwork has a very specific style or theme that has an specific subcategory for it, consider submitting it to the latter as it offers a couple of advantages I'll continue to explain.
Easier to find
As I mentioned above, an artwork correctly categorized will be more easy to find. Imagine you're searching for a Jack Frost cosplay photo. Obviously, you won't search for it in Digital Art or Fan Art, for you'll get a great variety of deviations of Jack Frost... most of them drawings or paintings... but no cosplay.
If you're searching for cosplay you'll obviously search for it in Photography (or Artisan Crafts) where you'll get a lot more accurate results.
So in this very obvious example, if you were to submit a photo of a Jack Frost cosplay and you submit it to Fan Art, potentially it won't be found by as many people as if it was in Photography, or not as easily at least, because the latter will be the obvious first stop.
Of course this is a very extreme example, but you get the idea. If you draw Manga, submit it to Manga! Not Digital Art. That way potentially will reach more people interested in the genre more easily.
Streamlines the DD suggestion and selection process
As you know (and if you didn't know I'm here to tell you, so now you know) in order to suggest a DD you need to send a note to the appropiate volunteer, for every CV is assigned to an specific gallery. What this means is that for as much as I like an Anthro piece which was suggested to me, I won't feature it.
So, if I receive a suggestion for an Anthro piece, even if it was submitted to Digital Art, I'll have to redirect the suggester to the Anthro CV and thus, the selection process gets delayed. If it happens to be selected, the Anthro CV will now have to move the deviation to the correct category before featuring it.
If you categorize your deviations correctly from the beginning and if someone happens to suggest it as DD, it will more likely be suggested to the appropiate volunteer from the start, the whole process will be less confusing for everyone involved and also quicker.
I'm not saying all this is magical. Not because your Fan Art artwork is in Digital Art it won't get noticed, or it won't be elegible to be selected as a DD, or on the other hand that if you categorize every deviation correctly it will magically get a lot more of attention... but it helps.
Think of it this way:
If you're looking for Manga artworks, where do you start looking? That's right! In the Manga & Anime category! Not in Digital Art. Same happens with Fan Art, Comics & Cartoons, Anthro, etc. So if your deviation fits in one of these categories, consider submitting to them. Sometimes something as simple as a category can make a huge difference!