I used to carry a multi-tool on each of my bikes. There's only one bike that has a multi-tool in its seat bag now. I love multi-tools! They're cool. I have expensive ones and cheap ones and now I don't use them hardly at all. Why? They simply do not work well as a real tool, when you need a tool to really work as a tool should.
Yes they have all of those sweet little tools in that nice compact carbon-sided folding swiss army-like frame and it even comes with a built-in chain breaker that doesn't work very well.
Yep, I have some of the very best multi-tools made. I now carry individual tools in the seat bag needed for the specific bike. Why? They work better.
Is it cool to carry individual 5mm and 4mm Allen keys, a Park chain tool, two tire irons and a small Phillips screwdriver? No. But when my bike broke down and all I had was my cool $100 dollar Lezyne Carbon-10 tool...it didn't work! Beautiful tool, truly gorgeous but it simply did not function well.
I now have individual sets of tools tailored for each of my bikes. They really don't add much more weight or space than the multi-tool they replaced. However, I bought a PB Swiss Tools multi-tool last year as a "oh what the heck" impulse buy.
Although it is a "multi-tool", it actually functions as a dedicated tool with swappable bits. Meaning, it works pretty darn well...and it has a tire iron! The jury is still out on this tool, and I keep it on one bike. It wasn't cheap either but it out-performs every other multi-tool I own. PB Swiss makes really fine quality tools...in Switzerland. I have a set of their Allen keys and they are the finest I have ever used. Better than my Bondhus Allen's, which are also very good tools.
I carry this tool and a chain breaker on the one bike and I'm confident that if I need it to really function, it will. This tool:
https://shop.pbtools.us/PB-470-BikeTool_c2.htm