Advantage+ Audience is the default for any objective, but you do have the option to switch back to original audience options. There are times when the way Advantage+ Audience works may not be ideal.
That said, don’t overthink this. Some advertisers resist Advantage+ Audience, and that’s usually a mistake. If you’re optimizing for purchases, you shouldn’t switch back. This is when it’s at its best. The algorithm’s only focus will be getting you more purchases within your budget, and you do not want to restrict that.
But if you see that your ads are routinely served to people who are much older than your target or to a gender you don’t serve, you may need to switch back. This is most likely an issue when optimizing for actions other than purchases since the algorithm would otherwise adjust.
Advantage+ Audience allows you to set a suggested age range and gender, but within Audience Controls, you can only set an age minimum and there’s no hard constraint for gender.
The algorithm will always try to get you more of the action you set as the performance goal. So if it’s conversions > purchases, that shouldn’t be an issue. For anything else, it could be.
If you are optimizing for anything other than conversions or traffic (which was updated recently), the original audience options allow you to select detailed targeting that won’t be expanded. Combined with the ability to select true age and gender restrictions, these tighter constraints may be necessary when optimizing for engagement-level actions.
Engagement-level optimization can be problematic regardless, but it is much more likely to go off the rails if you can’t set these basic limitations. It’s one of many reasons you should prioritize conversions when you can — and use Advantage+ Audience when you do.