It all depends on where your talents lay as an artist. Talented sculptors will handle 3D better, while 2D animators will perform much better in 2D animation.
From a game production stand point there is a big difference depending on the application of what you're doing. Here is a brief explanation:
3D excels in a longer running project, with a wider scope. 2D excels in smaller projects with a more narrow scope.
A 2D drawing is more effective when I do not need a large amount of things added. Lets say we have an RPG town, and we have an NPC. All he does is stand in one position. All he can do is talk to you. I may not even need animation. In this case 2D is much faster and more cost effective to produce.
Think now if I need a 3D model. This NPC needs to be completely, and accurately modeled. Even if only a few areas are going to visible, the whole model must be complete. Generally this means he should be animated too, as that detail will be expected of a 3D game. This goes for everything, even if only used in one location.
However, when doing a larger scale asset, such as a playable character. Say I have 30 animations, hand drawn. If I need another the artist must spend the time drawing the next animation, frame by frame. A constant consumption of resources. Now with a 3D model, as long as I have the model already done, all that needs to be added is the new animation sequence, which takes less time to do than the full drawn out 2D frames. All you are doing is moving points on a model, not drawing the frames from scratch.
Further more, if I have a character with 30 animations, and I want an alternate costume, thats 30 full animations that have to be redrawn, colored, and finalized. Even with an existing base drawing, it does not really cut down on the time spent. It is also incredibly expensive. Instead with a 3D model, you just have another model created, with the same animation anchor points, and it will fit in with all the existing animations. MUCH much easier, faster, and less expensive.
In summary:
3D models take a standard set rate of time to create as a base. Everything has to have this base level of time and energy spent making sure it looks good and is formed right from all angles. However once you have the model, the animation process is considerably less expensive and faster to work with. You don't have to make the model over again every frame of animation you have. It is EXTREMELY reusable.
2D drawn frames are quick to implement small props, as one single frame of animation isn't as time consuming as a whole 3D model. However that time spent on each frame adds up extremely quick. This costs a lot as you need more and more from the animation. In the long run, it will greatly out cost 3D animation every time.