The leather armor pieces he sells are the heavy type leather armor. In addition, they have build-dependant legendary effects that will definitely be useful accordingly. Leather armor is the most useful and imo, the best type of armor in game for late game purposes, first off because each piece offers a great ammount of energy protection (which you will definitly need later in game as you encounter more and more enemies wielding energy weapons), and that there isn't really that many perks and/or items increasing energy resistance except only one perk which needs a crap ton of endurance and level points to be spent for and a few edibles that will mildly assist you with that cause. On the other hand, there are a vast amount of perks and items that you use/consume to increase your ballistic damage resistance; therefore, the pieces he sells are a huge relief to survival characters so that they don't get shredded in higher level areas by gunners or super mutants that carry maxed out laser weapons and can easily 3-4 shot you. And in the none survival aspect of this thread, none of those perks and food items matter due to enemies inflicting radroach-magnitudes of damage. But ultimately, this was all my opinion and I fully respect yours, as well.