As for the glove comparison, Silvermoon are faaaaar superior to tier 5. They are a higher item level, have no wasted itemization points in strength and block rating (which is basically sub-par mitigation, only good when pushing for uncrushable without shield block), provide more effective health, and give 2 gem slots on top of already being superior stat-wise. If you're talking threat, you can even socket them with 2 8 hit gems and they will come out on top in terms of threat, effective health, and avoidance.
While the T5 does waste points on str and especially block rating, the block value is a nextremely efficient stat, and actually more than makes up for it.
I'll take the 44 BV + 16 str + 23 Block rating over an equivalent amount of itemization points in avoidance stats. The mitigation from the block value is significant, and it contributes to effective health.
The Kaelthas gloves are moderately better for effective health, that is true. But the T5 is WAY better for threat generation. Given both, there would be cases where you would use each one. And The Kaelthas gloves with two 8 hit gems are still MUCH worse for threat than the T5. 44 block value + 16 agi + 16 str is way WAY better than 16 hit for threat (plus that BV gives mitigation and the Agi gives dodge).
For me the deciding factor is the set bonus. The pieces are similar enough to each other in overall value from their stats, though they are good against different things. The T5 contributes to getting two awesome set bonuses, while the Kaelthas gloves dont.
If you flipped the stats, I'd still take the one that contributed to the set bonus.