I did some tests:
1) Call glVertexAttribPointer and glDrawArrays with GL_TRIANGLE_STRIP for every sprite (the original mode before to create this post), reaches 498fps. The stride here is 0, this mean that vertex position, texture position and color are in separate structures.
2) Cache the vertices in an array of 1024 structures. I'm copying the vertices that I'm passing to the cache with a memcpy. When the array is full, the content is drawn with glVertexAttribPointer and glDrawElements with GL_TRIANGLE_STRIP. I'm indexing the vertices here. The stride is 0. 589fps!!!
3) Same as above, but vertex position, texture position and color are on the same structure, this mean that I need to call memcpy to copy the sprite model, only once. I was expecting an improvment. 399fps.
4) Same as 4, but this time I'm unpacking the vertices from GL_TRIANGLE_STRIP to GL_TRIANGLES. I'm passing the 4 vertices and a function unpack them to 6 vertices. With this I don't need of indexed vertices. This takes much memory but the fps reached are 562!
5) Same as 3, but this time I'm using VBO: only 270fps.
6) Same as 4 but with VBO: 278fps.
Supposing that I'm not doing nothing's wrong, the best mode is the second. It doesn't take much memory and the indexing mode is easy to do. With this I can hardcode some basic models and indexing them. The vertex unpacking from STRIP to LIST can takes a lot of resources and it doesn't improve so much. I should avoid the structures all-in-one (I read from OpenGL documentation that it's implemented for D3D compatibility) and stores every attrib in a separate structure. For some reason, VBO decrease the performances and with this, SwapBuffer takes a lot of CPU. However all this methods are CPU-limited, because the GPU isn't totally used. Much of the CPU is drawined by memcpy and SwapBuffer.
EDIT: I tried the same tests with the same software without edits on another computer that handle a Intel HD3000 (the first tests run on a Radeon 4870HD): 62, 178, 124, 163, 97, 207fps. VBO with triangle list is much faster this time. I'm starting to be confused...