So let's start with colour. I would have definitely went for white if it wasn't for the new back design in iPhone 5. The white iPhone is shinier while the black used to be dull and more of a business iPhone. This kind of changed with iPhone 5. With the black and slate colour we get a cool pimped design. Just add a black privacy screen protector and you're done! The white is also seen as a cool colour especially with the silver back in the iPhone 5. Look at the comparison picture below.
It also seems that Apple believe the black iPhone 5 is better! They are promoting it in almost all pictures on their website. Here is an example of a catch picture.
Or it could just be because they have more black stock than white.
If you like to use headphones, then the white one may as well be a better option. Apple's new earpods look really cool with the white iPhone, a lot cooler than the black.
So perhaps the usage of earpods by you could affect your choice. You can also take it a step further and see which colour matches most of your cloths.
Now onto the space of the iPhone. You might be expecting that the 16 GB of iPhone is too little. But honestly it isn't. It depends on your usage for the iPhone. So if you are the type of person who downloads movies then 16 GB won't be suitable at all and you might consider the 64 GB. But just remember there is iCloud so you might want to consider that your movies could be saved in the cloud rather than your actual phone! I would recommend a 16-32 GB. Depends on how many apps you get and your experience on your usage from previous phones. Keep in mind that iPhone does not support SD cards, so what you buy is what you get.
The price of space to space varies roughly around $100 depending on where you buy it from. So think if it is worth it for you or not.
Have you got any more tips on what iPhone 5 to buy? If yes, then please make sure you share it with us. I'll probably go for a Black & Slate 16/32 GB iPhone 5.