Which "Pledge" combination is the most useful?

The title pretty much says it all. I just want to know which one will probably be best for competitive. I’m not gonna even use it, I’m just curious.

Here are the combinations:Fire Pledge + Water Pledge = Your team’s side will have the Serene Grace effect (x2 chance for additional effects from moves) for four turns.

Fire Pledge + Grass Pledge = The opposing team’s side will be damaged for 1/8 of maximum HP each turn, for four turns.

Water Pledge + Grass Pledge = Halves the opposing team’s Speed for four turns.

Out of these three combinations, which one is the most useful?(Also, sorry if this question was already posted, but DB didn’t show up with any similar questions.)

Pleaselog inorregisterto add a comment.

It depends on what you need. If you have Pokemon with a ton of moves with a second effect, then go for the Fire + Water Pledge. If you have Pokemon that abuse additional damage effects, like Rough Skin and Rocky Helmet, or Sleep + Nightmare + Hex, then go for Fire + Grass Pledge. Finally, if you have Pokemon that are moderately fast or a tiny bit slow that are outsped by most Pokemon, then go for the Water + Grass Pledge.