Although aptitude still has some bugs on bi(/multi)-arch machines, i.e. you install x64 on your machine but still install some packages in x86 for compatibility reasons; aptitude sometimes has dependency issues.
It's not a bug, but it is a problem. Aptitude's resolver is pickier. Debian has finally embraced multiarch systems and restructured x86 packages. It can still lead to weird dependency issues (but they're just that—issues with dependencies), but they're far less common and this strategy seems to have given them the confidence to include a lot more x86 library coverage than there once was.
