Approval Voting is better for 3rd Parties.

Approval voting always lets voters choose their favorite candidates regardless of viability. That’s great news for third parties and independents because that’s exactly what they need to grow...

Ranked Choice Voting has maintained massive two-party domination everywhere it has seen long-term widespread use. The most noteworthy example is Australia, where RCV has been used in their House of Representatives since 1918.

This seems to result from voters insincerely exaggerating their rankings. For instance, an RCV voter who favors a minor party will tend to insincerely rank his favorite major party candidate in first place. Why? Two reasons:

1. That actually is the best strategy with RCV.
2. Most voters don’t understand the mathematics of their voting system, so when faced with a ranked ballot, they will tend to use the “naive exaggeration strategy“. This entails looking at frontrunners and accordingly ranking one as best and the other worst, regardless of preference to other candidates.

Source: https://electionscience.org/library/approval-voting-versus-irv/