The real reason Vader chokes his inferiors is revealed in Ep. II.

Anakin says: The thought of not being with you, I can't breathe.

If you notice, the first person he chokes is Padme, the very person he was afraid to lose.

After that, he chokes anyone who crosses him, because without Padme, he can't breathe spiritually, and he wants them to feel a part of his pain.

When he finds his son, he doesn't choke anyone because he can breathe again, just a little bit.