Super Grub2 Disk
GRUB2 is a complete rewrite of GRUB, and Super GRUB2 Disk is a complete rewrite as well. As Super GRUB2 Disk uses GRUB2, the differences between GRUB Legacy and GRUB2 also apply to the different versions of Super GRUB Disk.
Perhaps the most notable difference between Super GRUB Disk based on grub legacy and Super GRUB2 Disk is that Super GRUB2 Disk does not write to the disk at all, and so cannot rewrite the MBR. Super GRUB2 Disk can only be used to boot a broken system, it cannot fix it directly. Though once a system is booted, re-installing grub is usually just a matter of running “grub-install /dev/sda”.
While there are some features of Super GRUB Disk based on GRUB legacy that will never be included in Super GRUB2 Disk, the opposite is also true. For instance, Super GRUB2 Disk supports booting OSX, loop booting from iso files, booting an OS from USB without USB support in the BIOS, and other features that are not possible with GRUB legacy.
Rescatux is a GNU/Linux rescue cd (and eventually also Windows) but it is not like other rescue disks. Rescatux comes with Rescapp. Rescapp is a nice wizard that will guide you through your rescue tasks.
About Rescatux and Super Grub(2) Disk
Super Grub Disk was a tool for fixing GRUB1 (version 0.9X) or booting into your system and it’s deprecated. You can still find its downloads although they are a bit hidden in Super Grub Disk page.
Super Grub2 Disk, contrary to Super Grub Disk, is not able to fix neither GRUB1 (version 0.9X) or GRUB2 (version 1.XX or 2.XX). However you can use it to boot into many systems including Windows, GRUB1 and GRUB2 based ones.
Rescatux is a Debian based live cd that lets you fix your GRUB1 and GRUB2 installations (as per Super Grub2 Disk lacks) but does much more.