From Pi-hole's perspective, there is little to gain by logging to ram.
Pi-hole itself doesn't rely on the logs, it uses its own in-memory structures to populate the dashboard for its current queries (rolling at 24 hours), and it pulls information from its database for long-term data display.
If you are just worried about SD card wear, buying a good quality SD card already goes a long way.
As mentioned above, you may also switch off logging completely, but that will also force you to use SQL commands against the database instead of e.g. tail and grep for plain text files to extract data.
Depending on your personal skills, that may not be a big deal, but you can't use SQL without knowing how the data is structured in views, tables and columns. Command line tools tend to be easier to handle, and more generic.
In general, I wouldn't worry about Pi-hole's contribution to wearing your SD card too much.
A single uncontrolled shutdown by pulling the plug on an RPi may do more damage to your SD card than a year of running Pi-hole.