As a Heathen, oaths are clearly pretty important to me. I think that the "legalistic" way of thinking about oaths is mainly useful for getting the one taking the oath to take it seriously and think it through, for one to avoid the kind of thing in SDI's example of skirting around the clear intent of an oath by following a lesser-thought-through promise. Also, as you imply in your example, overly broad oaths might bind you to something you're not actually willing to do.

As for the differentiation, I'd say "not really much, except in a narrowly technical sense." I'd treat all as giving my word under slightly different circumstances, but given the centrality of keeping my word to my beliefs, I hope I'd treat them the same. Easier said than done, of course, but I've tried to become more mindful of only promising things I feel confident I can deliver on, and I exercise even more care when making an explicitly holy oath, as the symbel boasts I've made on the new year the last few years.

Cheers,
Jeff