They are pretty similar. Both can be translated as "because and so". However there is a important difference about those two.

kara= subjectively presents a reason (it stresses more in the reason than other thing)

node= the same as kara but more polite and also stresses more in the cause-and-effect relationship as a natural course of events.

Therefore, node is not more coloquial than kara at all. In fact, is the opposite

@Wayne McGrath already gave you an answer about node and kara difference in meanings. However, I would correct his sentence with node.

nomimono wo kaitai NODE, mise ni iku ikimasu = I want to buy a drink SO I will go to the shop.

When you use node you always must use the polite form (desu/masu).

I would continue with the explanation but I think it's better for you to watch this video. It explains pretty well, difference between "node and kara".

https://youtu.be/G3_-LuElzfA?list=PLINFE8v4DOhsq0scG83kB5CRnowYWGSH7 (kara explanation)

https://www.youtube.com/watch?v=el5WhFUd9EE&index=8&list=PLINFE8v4DOhsq0scG83kB5CRnowYWGSH7 (node explanation)

This youtube channel is pretty useful for japanese learners.

Hope this helps.

This is a tricky one. The main differance between them is their English translation.

"kara" is translated as "because" where as "node" means "so". Take the following example sentences:

nomimono wo kaitai KARA, mise ni iku. I will go to the shop BECAUSE I want to buy a drink.

nomimono wo kaitai NODE, mise ni iku. I want to buy a drink SO I will go to the shop.

As you can see in most situations where you use one you can use the other. It's pretty much down to when you would use "because" or "so" in English.

Hope this helped!