No, this is not more secure; clients cannot view or change the content of (server-side) Scripts.
However, many programmers (including myself) prefer to keep all (server-side) Scripts inside ServerScriptService for organisational purposes. I find that having all of my Scripts in the same location makes development easier in the long run. To be more specific, I have one Script with several ModuleScripts; this way, my code is both re-usable and separated into logical parts.
Each developer has their own preferred way of doing things. You should just play around with a few different styles, and use what suits you best.
2 comments
Having it in the ServerScriptService means you can access the script from that place, whilst not being able to do that with the tool. It's not more Secure, but instead, more cleaner and you can get to the script in a more efficient way.
Server bytecode is not even replicated to clients but you should still put it in ServerScriptService nonetheless.