Hi there!

i have both! LOL! i wanted to try it all!

I have to say that i LOVED my ring sling (brand is Ellaroo - ellaroo.com i think). just fantastic! can't rate it highly enough.
when they are newborn they curl into a gorgeous little bundle and can nestle into your chest with their legs and arms tucked in (this was my girls fav possy for weeks). or they can be placed in lying down nestled against your chest (my girl didnt like this one too much unless she was really sleepy).
then, when they get more head control they sit facing outwards with their legs tucked up against their chest (doesn't sound comfy, but they LOVE it!).
then, when they get too leggy for that one, switch them to the side with the legs out the bottom. and that's the stage we are still using (she is almost 12 months old).eventually they go on the back.

DH wanted something he felt more secure with, so we went out and bought the ergo baby carrier. and for what it is, it's pretty awesome. bubs can do front, side and back. they are more restricted than the sling, but have way more movement than the bjorn (we borrowed one of a friend for a couple of weeks, and DD didnt like it very much). also with the ergo, the weight is carried more on the hips, saving the back and shoulders (which can come in handy for a post pg body and all relaxin ridden muscles LOL!). there is a newborn insert that you can buy for the ergo too.

they cost about the same ($130 from memory).

my pick is the sling (no buckles, no adjustment and can be folded up into the nappy bag, pram storage or in your handbag...and can double up as a blankie when on planes!)

HTH