O que é o aptitude “upgrade” a falhar aqui enquanto o apt-get é bem sucedido?

Question

UPDATE: adicionou why-not output como sugerido ( why output também).

# aptitude why-not libwbclient0
Unable to find a reason to remove libwbclient0.'  'why' gives this reasoning. 


# aptitude why libwbclient0
i   nagios-plugins-standard Recommends smbclient                                     
p   smbclient               Depends    samba-libs (= 2:4.3.11+dfsg-0ubuntu0.14.04.11)
p   samba-libs              Depends    libwbclient0 (>= 2:4.0.3+dfsg1)

Por que aptitude upgrade não está realmente atualizando o pacote enquanto apt-get upgrade está disposto a executar? Pelo que entendi, esses dois comandos devem ser funcionalmente os mesmos, mas obviamente eles discordam. Alguém pode explicar como encontrar o problema aqui e por que ele funciona para um comando, mas não o outro?

aptitude

# aptitude upgrade
No packages will be installed, upgraded, or removed.
0 packages upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
Need to get 0 B of archives. After unpacking 0 B will be used.

apt-get

# apt-get upgrade
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
The following packages will be upgraded:
  libwbclient0
1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 30.0 kB of archives.
After this operation, 0 B of additional disk space will be used.
Do you want to continue? [Y/n]