What's your opinion on SoB versus SoC as it pertains to Retribution Paladins (especially in PvP)?
Both scale based on AP and both can crit, so they are both potentially good Retribution Seals. Now, SoB does 35% of weapon damage every hit, and SoC does 70% of weapon damage at 7 ppm. If I assume a 3.6 attack speed weapon, you get 16 attacks (rounding down) in one minute. On average 7 of those will proc SoC. If you're doing 800 damage a swing (white, non-crit), you'll do 12,800 damage. With SoC 12,800 + 3,920 = 16,720 damage in one minute, without crits and ignoring all other variables such as miss, parry, glancing, etc... If you use SoB, you get 12,800 + 4,480 = 17,280 damage in one minute.
Theoretically SoB does slightly more damage than SoC at the cost of dealing a percentage of that damage to you. SoB is also significantly cheaper in terms of mana than SoC, and in a PvP environment is (in my opinion) more reliable, though the self-damaging component is more of a negative. Another thing I'm taking into consideration is how often Vengeance can be proc'd. It's essentially 9 extra attacks a minute that can stack Vengeance. Obviously, the usefulness of this changes depending on your crit rate, but I assume most Retribution Paladins are sitting in the vicinity of 30% crit.
Now, in PvE extra crits for Vengeance isn't that great - you get 3, and it's staying up until the mob is dead. The extra procs might get you to 3 marginally faster, but as the fights are much longer and more likely to be consecutive, it's not a huge deal. However, in PvP, where you might only be fighting one or maybe two people, getting to 15% is more important. Obviously, there's times in AV where there's plentiful targets, but I think the extra attacks are worth it.
Finally, the Judgment damage. It's higher on SoB in general, but you take a decent amount of damage, and with SoC it's fairly low unless the target is stunned. Which means if you start an encounter by Repentancing a target, then you can unload a lot of damage in a few seconds, but after that, it's barely worth Judging.
For now, I'm using SoB. My Judgments are higher and the damage is more consistent. The possibility of huge bursts of damage is nice with SoC, but anyone who's been fighting and had a string of non-procs knows that frustration, especially at 3.6 attack speed.
The final consideration, which is more of a PvE thing - is down-ranking the Seals, as the Seals themselves worth off of a percentage of weapon damage; only the Judgment portion suffers from lowering the rank of the spell.
I think you are fairly correct in your assessment of SoB versus SoC for PvE. However, I'm not sure that the extra chances to crit are really worth using SoB over SoC in PvP. Sources of crits include:
1. White attacks
2. Crusader strikes
3. Seal procs
You only affect one category of these by using SoB, and you give up burst damage, and you take more incoming damage. In my PvP experience, burst damage is what kills people. Not to mention that it's far more likely that people can be stunned for extra JoC damage.
As Vengeance lasts for 30s now, I think there are enough opportunities to refresh it, that using SoC over SoB will not hurt you. However, I have not really played in a high-resilience environment, so that may change things.
As for PvE, SoB is outright better than SoC. As you noted, it does more damage, and is more consistent. Additionally, the self-inflicted damage actually ends up having synergy with Spiritual Attunement, giving you mana back from splash healing, which increases your longevity. As well, SoB allows you to use the weapon with the highest DPS, as opposed to using the weapon with the highest damage range. That makes you a bit more flexible when it comes to gearing up.
Imo, SoB is a very good Seal. It is different enough from SoC that there are situations where SoC is better than SoB and vice versa. Really, Blizzard should remove Seal of Vengeance and give all paladins Seal of Blood.