[Solved] Problems upgrading systemd or udev, which is better

[program666]

I know there are a lot of threads about something like this already but none of them clarify some points about these packages that I'm really confused about. I'm trying to resolve some "preserved-rebuild" problems by emerging the needed packages myself, since "emerge @preserved-rebuild" will just spit out a lot conflicts anyway. The last big package I need upgrading would be "xmbc", and while I don't even need this to work (it's not really a emergency or anything) it tries to upgrade "udev" (or systemd, or both, I don't even know for sure).
Now, trying to resolve all the conflicts brought by this update is a adventure in and of itself, probably because I'm trying to upgrade a relatively old install, but my main concern is: what is the better system udev or systemd. Should I be trying to switch to systemd? I've seem a post somewhere that says that systemd was integrated into udev (here: https://forums.gentoo.org/viewtopic-t-964514-start-0.html), but I bet it's not true anymore is it? Or maybe the truth is even stranger than that?

What would be better? To keep udev, since I don't absolutely need systemd or to just move into systemd, since maybe that's the future anyway, and since I already have to solve this problem better solve into a more definitive solution.
On top of all of that you should bear in mind I don't even use the "init=" parameter on boot, I'm not sure if this matter but the grub entry for my linux install looks like this

[Tractor Girl]

Udev is part of systemd. For now it can be used separately without systemd but its current situation is somewhat blurry and causes constant confusion and problems.
To handle that, gentoo devs created udev fork: eudev. Eudev is and will be completely independent from systemd.
So if you don't need/want to use systemd and don't want to be bother with crazy stuff on every udev update, you should switch to eudev.

Here's little how to:

[program666]

Thanks a lot, this fixed everything. I had to remove virtual/udev after removing whatever package just using "udev" referred to but it worked.
Also thanks for clarifying the relationship between udev, eudev and systemd a little bit.

[program666]

I should probably create a new thread about it (and if so tell me and I will) but I have the impression that portage now refuses to upgrade anything ever, and lots of times it will give me "Multiple package instances within a single package slot have been pulled" for most upgrades unless I remove manually some old versions of packages.
Trying to run "emerge -av @preserved-rebuild" will result in these types of conflicts for the entirety of the Qt library. I might be wrong here but I think gentoo used to just update everything in these cases right? Maybe like 5 years ago but still.
I'm guessing this is to avoid breaking programs that make use of those libraries but what would be the correct way to deal with this? Is there a way for me to list every program that will be affected and upgrade all of them on a single emerge? Can I just say that it's ok to upgrade even if it breaks things (I was used to that actually, just needing to re-install stuff that was broken)? Can I mass-ignore and just tell it to keep the installed versions if it's not necessary to upgrade?

When I run preserved-rebuild this is the result:

[steveL]

[Tractor Girl]

Hey steveL
Thanks for adding me. I am frequent visitor to that thread of yours, many great advices in there.