If you always use the same body armor, get +3 body armor early (if it is lordly; do other things if you want to have one that tops out at reinforced). Any gloves besides leather gloves become "lordly" at +3 and give the same bonus as +3 body armor does. If you loom gloves first, you can play with many different body armors until you find one whose stats or appearance really fit you. If weight matters to your build FOR ANY REASON, gloves are always better to loom first. Even counting the x8 penalty for glove weight when you use ranged, heirloomed gloves are still more efficient than heirloomed armor.
+3 gloves are also one of the easiest +3 items to trade. If you change your mind, you can break even or get a profit trading +3 gloves for almost anything within the same day you put the offer on marketplace. If you have +3 lordly armor and +3 lordly gloves, that's 10 more armor with no increase in weight or repair cost. That's a huge difference even with 0 IF skill. Unless you are a master at blocking, heirloomed armor is a very tangible increase in power.
I still prefer to loom weapons first on any build, but that's my opinion. Even if the benefits aren't as big. If you can kill someone before they even hit you, your loomed armor doesn't matter at all.
On the other hand, my heavy armor longmaul build has +3 armor and +3 gloves. With 6 IF, the change from 7 + 53 (60) to 12 + 58 (70) means you can take about 10 hits in melee instead of 5-6. Your build and playstyle matter more than anything else when you are deciding what to loom.
edit: +3 armors make a huge difference, even on low weight ranged builds. If you can take 2 hits instead of 1, it lets you fuck up ONCE PER ROUND instead of being instantly punished with death for bad positioning or team support. Makes it easier to learn from your mistakes, since you can immediately act on them instead of waiting until next round to figure out what you can do to be better.