That’s a personal preference and there’s no right or wrong answer. Single cleanse means cleansing once, generally with a water-based cleanser. Double cleanse means cleansing twice – first with an oil-based cleanser (or balm/micellar water) and second with a water-based cleanser. Double cleanse could also mean using the same cleanser twice.
Some say that water-based cleansers are not effective in removing makeup and sunscreen. Most experts don’t always agree because a water-based cleanser can be formulated to be effective at removing makeup/sunscreen. So much depends on the surfactants used and its cleansing power. With the advancement in cleanser technology, many good water-based cleansers can effectively remove sunscreen/makeup without stripping your skin. Also – duration of cleansing can also play a role.
When chemists formulate a cleanser, the discussion on “if this should be a first cleanse or second cleanse” never really comes up. The only directions they follow is to ensure that the cleanser has the adequate ingredients (e.g. surfactants) to cleanse effectively. That means using the right type of surfactant technology.
Is there any evidence for oil based vs. water based cleansers?
There is only one study in the literature that basically showed that water-based cleansers and cleansing oil did not show a difference in sunscreen removal. However, cleansing oil did a better job at removing water-resistant sunscreen. This study is way too small (20 participants) to make a generalization though.
(https://doi.org/10.1111/jocd.12995)
Anyway, if you enjoy double cleansing, stick to it. Many find double cleansing to be more gentle and effective, especially on days of wearing waterproof makeup/sunscreen.