Some packages will be held back by apt-get until you "dist-upgrade" them and apt-get will notify you of the held back packages when you apt get "upgrade".
If you get a lot of packages that it tries to uninstall. That's basically what dist-upgrade does: tries to uninstall the least number of packages to allow the update through.
It never happens with a point release though - they are careful about that.
dist-upgrade does not mean distribution upgrade, it just handles additional dependencies after an upgrade and it may remove some packages if necessary.
There doesn't seem to be anything that jumps out as a reason to use aptitude over apt-get there. It mentions that the defaults for upgrading the distro are better for aptitude but doesn't say why or what differences there are.
I can see the search being useful though.
Seeing as my muscle memory is set at apt-get, i'll stick with it for the moment.
There was a brief time when aptitude was smarter than apt-get (it was smart enough to remove auto-installed dependencies when you removed a package, for example). During that time, the advice was to use aptitude instead of apt-get.
Those smarts were later moved to apt itself, but it's still a part of the folklore.
