There is no real answer unless you use a specific example. Art is a VERY broad term, because there are so many different types. Something like 3D modeling might not be very time consuming, but animating an object might. Even more so something like a spell animation can take a very long time. Something like concept art or texturing can be long or short as well. You just keep going to you get what you want.
Now coding generally can be long because it take the time to type it out and basically "connect" everything together and testing to fixed mistakes, bugs, and etc. Again, though, coding can be sped up when making similar things you can use coding to do that and make small changes.
There is no clear answer unless you can name things to compare, then an answer can probably be given.
You can also keep in mind that coding cant really be fixed by throwing more people at it, in fact the more people working on coding the more problems are likely to occur, because each person does things different and coding needs to all be the same. and everyone needs to be on the same page. While with Art long there are lots of different parts that can be split up and more people are normally useful. and you can get more similar results.