It’s the only sane choice:
* smart claimed that apt did not find all updates (due to its algorithm)
* then, smart is terribly slow (the solve stage taking >45 mins on an older 933 MHz machine)
* and overly memory-intensive (see Duncan’s blog post)
* referring to “breaking the interpreter” in the Ark post: it has happened to me; worth noting that you have to upgrade python (when SUSE moved 2.4->2.6) and its modules at once (but of course you could not have known that before, because dependencies were missing)
* zypper seems the be the only one to consider a vendor change a hard barrier, protecting against 3rd-repo packages sneaking in (IMHO even more important than any of the other points)