Different enough that a vaccine for one probably won't work on the others.
There are two genetically distinct types of HIV, HIV-1 and HIV-2. The two types are about 15-30% different at the DNA level. Both strains cause AIDS, although HIV-1 appears to be more virulent than HIV-2. There is some evidence that infection with HIV-2 may help protect against subsequent infection with the more virulent HIV-1. Epidemiologically, HIV-1 has spread around the world, while HIV-2 is mostly restricted to western Africa.
http://www.bioquest.org:16080/bedrock/problem_spaces/hiv/background.php I am not updated on recent progress on vaccines, but some years ago the problem was to find a vaccine that would produce significant numbers of memory T lymphocytes, which are important in killing an infection. I do not think that the efficacy of a future vaccine would be different for the subtypes of HIV-1.