I would like to stick to GRUB since it seems to be more actively developed and the entries are automatically updated after a kernel update. However I love the look of the Burg themes (especially sora_clean).
Are there themes available for GRUB2 which have a similar look? I especially would like a "folded view", showing only one entry per OS (by default), and a the installed OSes being shown as symbols, instead of listed text.
I would also be grateful for installation instructions along with the theme suggestions.
Grub does have some theming capabilities - we already have a great Q&A that covers how to change the Grub background and changing the text menu colours:
However, to answer your very specific question, it is not possible to convert the text selection in Grub2 to Iconised symbols. This is one of the reasons why BURG was created.
UbuntuForums has a great thread to cover Grub2 themes and more importantly screenshots showing the themes that can be achieved.
(post #61)
This screenshot was created by:
I'm loathed to duplicate such a great tutorial here as per the first post in the thread. Its pretty much self-explanatory on the steps you need to do.
For grub2 themes see: http://download-mirror.savannah.gnu.org/releases/grub-extras/themes.tgz
And http://apebox.org/wordpress/linux/261/
I don't have the time now but I will try to add full instructions for using them later.
In short, extract the theme directory (anywhere will do,
/boot/grub/theme_directory/
makes sense), addGRUB_THEME=/boot/grub/theme_directory/theme.txt
to /etc/default/grub and runsudo update-grub
.