Is this for skeletal animation? I'll answer presuming it is. #2. You typically wouldn't do #1. It takes a lot of space -- much more than you need to reconstruct joint transforms for typical animated characters on-the-fly quickly with reasonable accuracy. Also, #1 predetermines your frame rate, which is undesirable. Re your comment on averaging transforms, I'd highly recommend reading up on dual quaternions. Also the Animation section of Jason Gregory's Game Engine Architecture is a great primer for this (though it predates common use of dual quats in skeletal animation).
yes i'll use it for skeleton also for animating my 3d objects (car,air plane,..)wich moves static movement. so #2 will be better in gaming. thank you so much for helping