Veo 3.1 vs Veo 3.1 Fast

Same two aspect ratios, same 4, 6 and 8 second steps, same self-generated audio. A five-second silent take is 42 credits on Fast against 83.5 on the full model; with audio it is 62.5 against 167. On price alone Fast wins comfortably.

The difference that decides it is references. Full Veo 3.1 takes three reference images; Fast takes none. That means nothing about a Fast clip can be pinned to a character, product or look you already have, and a multi-shot sequence built on it will not hold together, however carefully each shot is prompted.

Both still accept a last frame, so frame-chaining works on either: render a shot, take its final frame, open the next take with it. That is a weaker form of continuity than reference images, but for b-roll, establishing shots and anything where the subject is not a specific recognisable person, it is usually enough.

So the rule is about the sequence rather than the shot. One clip, nobody who has to look like themselves: Fast, and take the saving. A run of clips that share a subject: full Veo, and do not try to economise your way around it. If you want a *silent* clip cheaply, Fast is also the answer, because Veo 3.1 Lite has no silent mode at all.