Moderator note: Product discussion so moved from the VCAP forum area to the ESXi 5 forum area.
HP was divided into two companies a few weeks ago, HP and HPE (HP Enterprise), so this is just a naming thing for the images you mentioned. The difference between ESXi 5.5 U3a and U3b is the build (i.e. the patch level), and you should opt to the latest in this case.
Install the latest patch u3b
Hi a.p. and JinuV,
Thank you both of you guys.