Does this GOG version come with unfinished business? Because the Steam version does which is Gold. Isn't GOGs version gold too?

Lastly does this come automatically patched to 1.13?

I am not sure if UB is included, but 1.13 is a fanmade patch/mod, so probably not.

JA2:UB is a separate game for GOG. Technically speaking, they actually are separate games, even if JA2:UB was sold as an expansion, you don't need JA2 to install or run it from the original disks (nor GOG's versions, of course).

You can buy JA2 and JA2:UB or any one of the two; while in Steam you have to buy "JA2 Gold" which includes both. Even at full price for the US, GOG's JA2+JA2:UB costs the same as Steam's "JA2 Gold", and they are both discounted at GOG right now.

GOG's JA2 is Gold and comes patched to the latest official version, which is 1.12. (Source)

1.13 is a fanmade mod, and as such they would need to get the permission of the creators as well as permission from the current owner/publisher of the game to include it, and then go back on it if any of the two changes their minds (like it happened on Steam, pissing people off left and right) ... waaay too much of a hassle for a distributor.

As a general rule no modifications are included with GOG games except very few exceptions, and usually only when they are absolutely needed to be able to run the games in newer systems and OSs (like alternative D3D wrappers, etc.).

Which version is better? Steams or GOGs and why? Without bias. Thanks.

That something is better than another thing is a biased opinion for any human being. And I certainly am one, and not a perfect AI :P. There is no opinion without bias I can give.

All anyone (being honest) can do is present facts about the games and about the distributors.

I already stated the difference in "packaging" between the two distributors. The game's content is the same as far as I know. The differences between the distributors themselves are too many to single handedly explain in a forum post; you should do the research and processing of the differences yourself for it to be of any value in your selection process.