You get '=' with 'shift 0' on german keyboard.

If you remove packages with Synaptic or with aptitude, they are gone from their directory, for example '/usr/bin/gimp'. Synaptic and aptitude/apt uses '/var/cache/apt' and '/var/lib/apt'. Parts of this remains in the HD Installation, but will be omitted in the new ISO. Have a look in the script 'kn-rsync'.

Therefore it doesn't make a difference using Synaptic or aptitude in aspect of the size of the ISO.