I chose the third option (50/25/15/10), strictly because of the following statement in the OP:
The poll assumes both attacker and defender are of equivalent levels in every aspect.
And in that situation, winning a fight should boil down to a couple of primary methods: tactics - the PC (or NPC, the bad-guys can win) uses their knowledge of the Enemy, and/or their own fighting methods, to come up with a tactic to gain an advantage (in game terms: a bonus), or just hope to get a lucky roll. (I prefer it if the players go for the tactical option because it means they are "into" the game more.)
But those numbers only apply in that specific situation, when you have the PCs going against mooks (the unimportant troops) it is more like option 5 (10/30/30/30). For "High Adventure" gaming I think it would behoove you all to check out 7th Sea, as that game I think is a perfect example of how that type of game should go. The real funny thing is, I don't think of Harp as true "High Adventure", but just a more player-friendly and easier to learn/play Rolemaster, though an argument could be made that
compared to RM it is high adventure.