H.,
A few thoughts:
1) Infantino was recently sued bc. a baby passed away inside of it. The sling cut off the breathing of the baby & the baby couldn't/wasn't strong enough yet to readjust. I am in my 3rd trimester as well & am hesitant to suggest a sling.
2) The wonderful thing about the wraps is that they center the baby weight on your body. If you are sensitive to your own body alignment you might particularly enjoy this. I found slings difficult for the reason that I felt like my body was out of alignment after a period of wearing the baby in it; I felt like my body was compensating for the uneven weight distribution & that caused further tension in my body.
Personally, I used the Bjorn, the Moby & Ergo with my first. (I was lent a peanut wrap sling & a ring sling & they didn't work for me primarily for the reason above, -alignment of parent & babe - but also bc. I didn't like not being able to see the baby. I also felt like the sling buried the baby & it seemed like it would be difficult for the babe to readjust due to the pressure of the sling. I just didn't feel confident with the sling for baby's mobility. In most wraps, the baby has more ability to adjust it's movements bc. it isn't restricted by the sling. I also felt like the wraps were better for the babe's alignment.). Here's my two cents:
Moby:
Pros: a) body alignment in mother & child b) since the baby was as close to my body as possible, it was the most comfortable & therefore it was easier to carry the baby for a distance. This was a big benefit as the baby grew & I wanted to go for hikes. c) it is really soft & comfortable. d) good for all ages, birth to a few years. d) front & back wearing. e) doesn't splay babe's legs. There are a variety of positions you can use. f) no buckles to malfunction.
Cons: a) takes practice to wrap & time to put on.
Ergo:
Pros: a) it's got a safety latch, so if the buckle malfunctions you have time to fix it without your baby falling out. This is a big plus for me. b) it is really convenient. When I was popping in & out of stores this was the one I used bc. I found wrapping the Moby time consuming. (However, as other posts have noted here if you wrap the Moby once you can keep the Moby on & still pop the babe in & out. I did try this & found that I couldn't get the tightness that I wanted the second time, but maybe I need to practice a little more.) c) It has a baby insert to be used before the baby can splay the legs around Mom. I can't vouch for it bc. I didn't use the Ergo until our daughter was old enough to wrap her legs around me. d) again, awesome for my body alignment.
Cons: a) can't nurse in it inconspicuously.
Bjorn:
Well, you've used one so you know...but for comparative sake...
Pros: a)I found it awesome for convenience, but as the babe got heavier, as noted with other posters, my back was yelling at me. b) great for parent & child posture (provided the babe isn't facing out prematurely)
Cons: a) no safety latch. (I saw a buckle malfunction which has since caused a couple of hospital visits for the babe. It has got me quite nervous about carrier safety. I am trying to see if I can sew a safety latch on to my Bjorn before this babe arrives.) c) no inconspicuous nursing option.
Personally, I've got my Moby washed & ready for babe. (I'm due in 4 weeks). Same goes for the Ergo...& I'm trying to figure out a safety latch for the Bjorn. If you can find space & $ for both, they are both helpful.
Hope it helps. Happy baby/toddler wearing
K.