🔥 or 💯?

🔥 praises the thing, 💯 endorses the statement.

🔥

Fire U+1F525

Fire – excellent, impressive, "this is hot" in the figurative sense.

When does it fit?

Under photos, music, results.

💯

Hundred Points U+1F4AF

A red 100 – full marks, complete agreement, "exactly this".

When does it fit?

Agreeing with a statement.

The difference in detail

🔥 says "this is great" about something shown: a photo, a song, a performance. 💯 says "exactly, full agreement" about a statement.