In an Armory tutorial on youtube Andy said he useing ubuntu. But not much into why he did it. When searching Im most finding installation problems. Perhaps I can do a better search. But how come its better to use it when even if the computer is cold?
A cold windows computer should be that secure as ubuntu?
Yes, the OS doesn't matter, the main thing to understand is as long the computer is offline it is safe but he might have mentioned it because usually the computers people don't use for online purposes are old and have less ram and cpu power and which is why ubuntu or other linux distros are recommended as their older versions work well with computers with less powers, also they can be run on a pen drive very easily which is very hard to achieve even if you're trying to run xp. But even ubuntu require some knowledge and experience to use so if you're not comfortable with it just use xp or seven or which ever one you want to use as long as your computer supports it. The only thing you need for a cold storage wallet is a computer capable of running a browser with java enabled.
Really above all else, the point is to do a fresh OS installation on the computer. If it's been previously online who knows what kind of malware lurks on it (especially if it's running Windows.) Ubuntu was chosen because it has the largest userbase among desktop distros and the install is probably one of the simplest.
Honestly I've found Linux installs to be easier than Windows installs. The main pitfalls people run into are in getting certain wifi cards and certain graphics cards to work. Neither are needed for an offline Armory wallet. In fact it's even better if your wifi card won't work because then it's impossible for any app to connect to anything. In the case of the graphics card, likely all you'll be lacking is OpenGL acceleration because if all else fails Linux will fall back to the VESA framebuffer driver which will work on damn near anything. This will still bring up the Xorg GUI and worst case you'll have to live without some of the transparency desktop effects. Who cares! The offline wallet is for signing transactions securely, not for looking pretty!
For older computers, look into Xubuntu and Lubuntu instead of the main Ubuntu. They use the exact same package base (even pull from the same repos.) The only difference is in the GUI. They use Xfce and LXDE, respectively. Lubuntu is going to be the lightest of the two. Xubuntu, IMO, looks much better but may use a little more RAM. Both are much more lightweight than Ubuntu with its default Unity interface. Perhaps the biggest difference is that Unity has no way to turn compositioning off (the thing that enables the fancy desktop effects.) This means that if you run into problems with your graphics driver like I noted above, Unity will fall back to llvmpipe which attempts to render all those fancy effects on your CPU. This works but will be much, much slower (and probably unusable if you have an older CPU.) On Xubuntu you can simply turn off compositioning (if its enabled by default) to have a fast GUI without desktop effects and with Lubuntu I don't think compositioning is even an option in the first place.
It's open OS so i think there no hidden bugs from NSA 
