Which is best for hacking : Kali Linux or Ubuntu?

By just concentrating on operating system, you won't learn hacking, no matter what operating system you use, you need to understand the concept of your topic in hacking, Hacking is a very, very large field, Hacking has various categories, which you first make interest of, like, as we have doctors, who are specialized in one thing, like, heart specialist, eye specialist, skin specialist etc., similarly, we have, OS security, Network Security, application security, etc.,

Instead of concentrating to use a particular distribution of Linux, if you do really interested in hacking, first build your interest in any of the particular concept, not limited to only one, but first you should know basic of each of the mentioned about security concepts, and then move forward to which you get most interested at that point. You could start with any of hacking challenges website like, HackThisSite, which has basic to advance hacking challenges, which may give you an idea on various concepts of hacking.

As far as choosing, any of the operating system (*nix), let me clear you some facts. Ubuntu and Kali, both are Debian based OS, you can install all the tools available in Kali Linux on Ubuntu as well, the pain of installing those tools reduced as Kali comes with bunch of tools, I dint known any of the hacker who would have used all those tools on Kali, most of the tools are duplicate for one purpose, for example, for SQL-injections, its your personal preference to either use, SQL-map or SQL-ninja. Similarly there are plenty of tools for one single purpose.

I used, BugTraq II black widow, for couple of years, as it has even more RATs/Bots and shells pre-installed. The point is, you can use any distro, of your choice, and you can install the tools which you needed.

-@Gopan Samantaray:

I am a cyber Crime investigator, as far as forensics is concerned, Linux stand too far of it, as the commercial products like, Encase, FTK, BlackBag and Cellebrite/UFED(Mobile Forensics), has excellent features when compared to any of the forensic tools on *nix. but, for basic forensics. For in depth analysis, its not a go.