功能上的区别：
http://www.debian.org/doc/manuals/debian-faq/ch-pkgtools.en.html#s-aptitude彩蛋上的区别：
$ apt-get moo
(__)
(oo)
/------\/
/ | ||
* /\---/\
~~ ~~
...."Have you mooed today?"...
$ aptitude moo There are no Easter Eggs in this program.
