the higher the voltage - the more of a spark you will get when connecting the battery each time. Or turning it on. Usually i’d suggest if you are 8s-12s range to use anti-spark switch or anti-spark loop key. You could also use it for 6s, but i don’t feel it’s quite as needed. Each time it “sparks” it wears away some of the metal, so over time your switch and battery contacts will wear/erode away eventually.
Simplest solution - an XT-90s anti-spark loop key. Stupid simple and a fun quick project if you have a decent soldering iron, some basic solder skills, and a few minutes of time to spare:
A push button anti-spark switch is also nice. There are a few from Enertion, DIYes, Ollin BC, MEB, esk8.de that vary in price. Personally i really like the v1.3 and newer v1.4 Vedder/Fechter anti-spark switches. Myself and @DeathCookies have a few “kits” left (you assemble yourself from components), or you can buy one from the above.
Ultimately it boils down to a $5-10 loop key, or electronic switch for a bit more.