Honestly, I think you have a lot of options open to you...the Bjorn and Snuggly just don't do the best job of weight distribution and because of the way the straps work tend to be hard on lower backs and the OTSBH is a pretty hard to adjust ring sling and the shoulder just doesn't give the best spread, IME.
With a newborn, I would recommend a stretchy wrap for you...the Moby Wrap is really, really wonderful. Easy to use, super comfortable. It is not super fast to get on...6 yards of a super soft t-shirt material that you wrap around youself and tie...but not hard to do at all and once you get it on, you can pop your baby in and out as needed. The wrap gives wonderful weight distribution and support for lower backs and shoulders.
You also might want a really wide shouldered ring sling for just quick carries...the Maya Lightly Padded is my favorite for that but the EllaRoo Lightly padded or Pretty Mamma Ring slings are great as well...I think you will find all of these more comfy than OTSBH...I know I did anyhow-LOL.
As your baby gets bigger, you might want to think about a woven wrap like a didymos, ellaroo, hoppediz, storchenwiege, easycare exc...I really love the Moby with a newborn and really for front carries for most of the first year and they are great when you are first getting started with wrapping...but for back carries and with a bigger kid, the wovens are definitely more supportive.
Another really great option for lower back and shoulder issues ar the Mei Tais...they do a wonderful job of spreading weight to the waist and hips and all across the shoulders and back. They don't happen to be my favorite with newborns though but once your baby is a few months, they rock, IMO. The weight distribution is not quite as good as with a wrap but a Mei Tai is much easier to get started with and much less to deal with in general.
Hope this is helpful!
Alison