My completely unqualified position is that manjaro is not more stable than arch, in fact, according to the news manjaro's changes are just more instability. I've been running basic arch & KDE for 6 months now and it hasn't been perfect. The biggest issue I've had so far is; "using the scroll wheel in the KDE start menu will crash the DE" and that was fixed in a day.
Arch Linux
The beloved lightweight distro
According to Debian users, "stable" means "unchanging" and not "doesn't crash or have bugs" ... If you still ship 100% of the changes but just delay them by 2 weeks, you have the same number of changes. So by the Debian definition of "stable", no, it is the exact same as arch.
By the everyone else definition where "stable" means "doesn't crash or have bugs", then also no. Shipping buggy code 2 weeks later doesn't reduce bugs. And if you use the AUR at all, then things get worse, I've found, as the AUR pkgbuilds expect dependencies to match current up to date Arch repos.
tl;dr - no
No, because the whole Manjaro concept is bullshit.
Delaying updates by two weeks for a few more checks could help catch some bugs that went unnoticed, but not in the way Manjaro does it. Which means with no rhyme or reason at all. They don't use the two weeks for additional tests. They don't even collect fixes or patches based on the bleeding edge experience of actual Arch to apply to their delayed updates. They just delay updates, fixes and everything by two weeks. So your system is exactly as unstable as Arch just with 2 weeks delay.
And it gets worse from there: Arch has a disclaimer about the AUR being unsupported and requires you to install AUR helpers manually, so you did it at least once the old-school way and actually see the disclaimer. Manjaro however gives you access to the AUR pre-installed. No, not a cloned version of the AUR that is also 2 weeks behind. Direct access to one as used by Arch that expects your system to be up-to-date, not 2 weeks behind... introducing a completely new kind of dependency hell and instability.
PS: And that's before questionable stuff on the Manjaro side... like letting their SSL certificates expire multiple times (and suggesting changing your devices clock as a "fix") or DDOS'ing the AUR with a bug in their AUR helper, also multiple times.
☝️ This! I have no idea how Manjaro became so popular. One of the worst Arch-based distros imo. Lets take Arch and hold back packages, thus causing dependency issues, and even OS failures. Welcome to Manjaro! Sigh
The delayed updates also include security updates by the way, so you're vulnerable for two weeks to any known exploit.
Manjaro was worse when I tried it a few times. I'd steer clear of it.
I will note that your "I have no way to know how many problems it would have it I used it every day" is kind of.. the stability "issues" is due to frequent updates. You can simply not update for a few weeks at a time, reducing the likelihood of encountering issues.
I find Arch more stable since I choose what to install and everything is basically "stock".
However my experience with Manjaro is from a few years ago, it could have improved.
nope, just older. and as soon as you throw in AUR you're asking for trouble