So your comments are more aligned with how tanking worked in the burning crusade or how ret pally's switch seals. While some pally's do chose to spec into reckoning, it does not meaningfully increase threat or damage compared to the alternatives that you have for those 5 points.
Both of the builds that you posted have slight errors in them, so I'll post 2 valid builds and try to explain the differences:
A 'pursuit of justice' build Talent Calculator - World of Warcraft
A 'seal of the pure' build Talent Calculator - World of Warcraft place the last 2 points by personal preference.
In your pursuit of justice build, you had 2 points in judgment when you only need 1. In your conviction build the threat/dps you thought you were getting from conviction would be better placed with seal of the pure.
The biggest thing missing in your personal build is Judgement of the Just. It is the single best mitigation talent for boss tanking (on a point basis) in the tree. Its a must have. Slowing down boss attack speed=reduced damage. Nothing else gives you 10% reduction per point (math works out to be slightly differently, but conceptually close).
Reckoning gives you a slight boost in threat, but not as much as the SotP build if you are having threat issues. You should always be running with SoV/SoB and be glyphed for it as the expertise boost from the glyph is great for both TPS and damage reduction. You should also have glyph of judgement. The only real exception to that is when you massively overgear the instance and want to run SoW because you aren't getting hit and thus don't need heals.