I'm using PyOpenGL to implement a small 2D game engine. I'm hesitating on the way I implement a Sprite class.
I'm already keeping all the scene (tiled map) in a VBO, and all textures are kept in the same big texture. All the sprite's images are also in this texture. So I suppose that, for performance, I should include the sprite in the VBO, let say from position sprite_start_position.
The first question is : since a sprite can have several stances (images), is it better to :

setting only one entry in the VBO for the sprite, and modifying the texture coords in this entry accordingly to the stance, using glBufferSubData
setting as many entries in the VBO as there are stances, but drawing only the current one with glDrawArrays 
other ?

The second is the similar with sprite position. Must I :

change the position of the right entry in the VBO with glBufferSubData
use some glTranslate before glDrawArrays(GL_QUADS, sprite_start_position, 1)
other ?

I'm relatively new to OpenGL and I still feel a little lost in this API...
You really shouldn't have to worry about performance for simple sprite based 2D game. Your graphics card is capable of rendering tens or hundreds of thousands of triangles per second (or more!) which is way more than you are likely to need.
Thus, it really doesn't matter much which method you choose to use for updating sprites. If you want to have animated sprites though, I recommend you look into 3D textures. They allow you to interpolate between animation frames, which makes your animations look even better!
As a side note, you mentioned using glTranslate which is a function from OpenGL 1.x/2.x that has been removed from later versions of the API. I recommend that you try to use "modern OpenGL" (ie OpenGL 3.x/4.x). You can find plenty of information about the differences online. That said, it is still OK to use the older versions of the API if you have a specific reason for doing so,  and if you do functions like glTranslate will continue to work.
Fastest way to implement a sprite