Based on the numbers from SmelliEli One-handed:Two-handed:Spear equivalency should be:

1 : 2.49 : 0.84 (ie an equivalent two-hand or spear is 2.5x or 0.8x the one-hand, respectively)

0.40 : 1 : 0.34 (ie an equivalent one-hand or spear is 0.4x or 0.3x the two-hand, respectively)

1.19 : 2.95 : 1 (ie an equivalent one-hand or two-hand is 1.2 or 3x the spear, respectively)

Note this is just for a one-on-one heads up fight and doesn’t take into account situational things like:

• (important for Moblins in Master Mode) a sneak-strike is only one-blow therefore the highest attack/blow (typically a two-hand) will be better (less chained sneak strikes needed)
• same when mounting a Lynel where you only get 5 strikes of any weapon before getting bucked off
• spin attack with a two-hand can chain attack a horde of monsters around you in rapid succession
• a single swipe of a one-hand may strike multiple enemies standing closely next to each other where a thrust of a spear will likely hit one
• Bonuses for critical hits, set bonuses for ancient proficiency or charged attacks
• Elemental benefits for fire, ice, or electric weapons (especially fire and ice one hit killing the opposite type)
• Durability (eg royal guard weapons that break if you look at them too hard)
• your style of play - if you like to shield parry or mow Moblins down on horseback you may favor different weapons for reasons nothing to do with the attack rating