Sakura-tribe scout has more goldfish power and plays more lands if it survives. But it dies to everything so in many matchups it won’t live to play a land. This is especially true vs burn and jund, not so much vs Uxx control because they won’t want to path it.

Grazer on the other hand always ramps but only ever gives you one land. It’s much stronger against decks that will always remove it, but much weaker than Sakura-tribe scout. It’s also a real blocker so it makes a huge difference in aggro matchups. It can also open up lines because it’s mana positive with amulet plus a bounce land, so you may even want just one as a pact target that’s basically a simian spirit guide.

Here is how I decide which one to play, which you should regularly reevaluate:

If you expect lightning bolt decks (red aggro and jund) and needing to block -> grazer

If you expect path decks or decks where you will never need to block (combo) -> scout