Accessory buff comparison
Comparison table on JP wiki
+Affliction rate (+2%) is the best effect for Single-element builds. You want this on any ATK or DEF debuffer whose abilities ever miss. Debuffs missing is the #1 reason for wipes in content you can usually clear, so less missing = fewer wipes. Since DEF down is directly linked to damage output, 2% less chance of missing > +2% damage, which makes +Affliction rate superior to even +ATK for damage when equipped on your debuffers, and since debuffs typically have a team-wide effect you can multiply that by 5!
+ATK (+3% max) has a 0.45% return in damage for each additional 1% at 120% character ATK, or +1.35% damage for a max-level accessory. As a rule of thumb, take the nominal effect and divide by 2 for the true effect on damage. Good on any character, but the effect is small.
+Double attack (+2%) directly modifies normal attack damage and can modify Burst damage as well if it contributes to more frequent Bursts. As such, it's best used on frontliners. Using a build with Shiva where the damage breakdown for normal/skill/Burst damage was 51/20/29%, +Double attack adds 1-1.6% damage, depending on whether it's contributing to more frequent Bursts or not. That range will also fluctuate somewhat depending on skill damage contribution to overall damage. On a bottleneck character double ATK would be better, while on others +ATK might be better. As a rule of thumb, take the nominal effect and divide by 2 for the true effect on normal attack damage.
+DEF (+3%) decreases damage by a little less than 3%. Use this to enhance survivability of vulnerable frontliners or essential characters, especially with low HP and no DEF bonuses. Use this over +HP% when possible since it benefits more from healing. Otherwise, the same caveats as +HP% apply.
+HP% (+3%) is straightforward. But you should already have +HP from Defender weapons, so the effect will be somewhat reduced. Only recommended for kamihime with low HP or frontliners. Otherwise use Defender weapons and eidolons to manipulate HP for your entire team at once.
+Drop rate (+1%) is valuable for farming. Assuming you like farming efficiently, having these in your progression gear isn't a waste. Make sure you keep all Rs with this, as they're free to unequip.
+Mode gauge reduction (+4%) is useful to end Rage quickly. Mainly for solo progression content, and useless on everything else. If you’re having trouble clearing Accessory Quests, stack this and aim to push the final boss into stun before the 2nd Overdrive.
+Ability damage (+5%) is worse than +ATK for SSR skills with less than 3 hits (which is the vast majority). Why? For starters, the base modifier should be < 3.7 to compete with +ATK. If we're going to buff abilities and nothing else, we want to see at least a 2x difference, so reduce that to < 2. The ability should also do significantly more total unbuffed damage than a normal attack to be worth buffing, i.e., 4x (which disqualifies SR characters’ weak damage skills). Divide 4 by a number less than 2, and a minimum of 3 hits is required for a significant effect.
+Burst damage (+5%) is useless because, like +ability damage, it adds to a modifier that is already greater than 1. For SR+ kamihime, that's 3.5+, essentially nerfing the effect to the same as +ATK or less. Burst builds can expect even less return since they'll be using temporary buffs to raise that base modifier even higher. This stat exists to trick players who don't understand the damage formulas. As a general rule, take the nominal effect and divide by 5 to get the true effect.