I am going to go against the grain here and say that for some thing 3d is easier. Currently my game is 2d sprite based (my own code, shader based). But i want say simple animation, like a aircraft banking in turns... this is pretty easy in 3d, but in 2d the animation systems get complicated fast, and sometimes just impractical.
But restricticing yourself to 2d is a good idea for at least the start. I am not switching yet. We are going to go for some stylized art and game pace that removed the "wrongness" of things like banking in turns...
I'd say 3D is harder. Just because you need to do real modeling if you want to program real 3D games.
Making 2D Sprites is much easier than modeling 3D objects in blender for example.
(also, if you want, you can also create a model for your aircraft, then render images of it with different animations. Then put the aircraft into your game as sprites. It works and is often used. If you are able to model objects, or are modeller...)