I wasn't sure myself so I did a quick search and the only thing I found was that ので(node) is more formal and sounds softer than から(kara). If you're not aware it should also be mentioned that から also has more functionality than to be used for an explanation. It can tell a from place/time for example アメリカから来ました。(Amerika kara kimashita) means I came from or am from America. While I'm pretty sure you wouldn't say アメリカので来ました。 (Amerika node kimashita). Kara can also reference when something starts 学校は８時１０分から始まる。(Gakkou wa hachi ji jyuu pun kara hajimaru) School starts at 8:10 am.