Christer Edwards explains why he uses aptitude instead of apt-get in his Blog Ubuntu-Tutorials
“First of all you might have noticed that all of my tutorials use the command aptitude instead of apt-get. The reason for this, from my understanding (and perhaps some of you can address this in a bit more detail) that aptitude handles dependencies better than apt-get.”
Personally I prefer to use apt-get, because the power of aptitude is sometimes too much, specially for the unexperienced user. It can whipe a whole set of packages just to resolve a dependency. In my opinion apt-get upgrade is safer to use and with harder to resolve dependencies apt-get dist-upgrade has my preference.
apt-get – f install and apt-get install –fix missing are also powerful and fairly safe tools to resolve problems.
If aptitude is needed to resolve dependencies and other problems its likely the package is not really matching your specific distro and it might be even wiser not to install the package at all.