As far as I know, ubuntu live usb versions use syslinux as bootloader whereas, when installed, the default is GRUB2. This makes replicating the boot experience a bit more involved than just copying the config files.
1. It appears a splash image, purple with a symbol on the lower side of the screen, which shows you how to intervene in the boot process
2a. If you don't press any key on the keyboard in like 15s, the bootloader goes on booting the default session
2b. If you press any key you are shown a menu where you could "tweak" the boot process (set language, what to boot, etc.)
GRUB2 default boot-experience with multiple OSs:
1. It appears a menu with all the bootable images 2a. If you don't press any key on the keyboard in 10s, the bootloader goes on booting the default session
2b. If you press any key you can actually choose which image to boot
What I'd like to do is hiding the GRUB menu to show a splash image identical to the live one and then, if I press a key, to be presented the full menu. Obviously I don't like to extend the boot time so the splash image timeout would be the only one to wait to and on the other hand when the menu is shown (which would happen only if I press a key) the timeout would be futile, 'cause I'm already in front of the computer to select the image I want to boot.
Hope to have been clear enough.
I already tried editing /etc/default/grub, toying with
GRUB_TIMEOUT and splash images but I had no luck. Yes, I used
update-grub after every edit ;)
I looked deeper in the internet and I found there are several problems involved: