Does Matter matter (compared to devices flashed with third-party open source firmware)?

I'm just getting into home automation, so I don't really know what I'm doing. I care a lot about supporting open standards (which is partly why I never bothered with it until now that Matter is coming out), but I also very much like the idea of having everything I own running Open Source firmware instead of whatever potentially untrustworthy stuff it comes with.

So anyway, I got some TP-Link Kasa smart plugs (KP125MP2), but have since been doing some more research and found that some folks don't think there's actually much, if any, advantage to Matter devices compared to older wi-fi devices that've been flashed with Tasmota or ESPHome. So now I've also got some Sonoff S31 smart plugs and a USB to serial adapter to flash them with, and I'm wondering which set of things I should actually keep.

I kinda feel like I need to try installing and using them to know which I prefer, but I'd also feel bad about returning stuff after it's got provisioning info stored on it (or worse, flashed firmware). So maybe I can decide based on advice y'all give me instead?