I'd say learn how to use the padded one for now, then get and Ergo and later a Hip carrier.
Mothering magazine did a special on how to wear slings.
(Goggle for "Mothering How Wear sling") - the babies usually look scrunched, but comfortably snug.
More advice here http://www.kangarookorner.com
they have lots of advice about various slings, comparisons (front/back? padded/non-padded? discreet nursing? weight requirements? OK for pool use? etc) and they sell several. The maya sling is well-know for being one of the most versatile, but I never got the hang of it too well. (About $29). I got a fleece pocket sling (from kangaroo korner) - which was very easy to use, nice in cool months or inside (NOT outside in the summer!) But it didn't work as well when he was old enough to ride on my hip. (Maya's pretty good for that)
Later, I got an Ergo carrier. You can start using that one when they're old enough to hold up their head a little, carrying them on the front. (Always facing in, never out. But arguably, those outward-facing carriers like Bjorn can be a little over-stimulating for them.) When they're older, you can carry them on your back! It took some practice getting him on my back safely all by myself, but the beauty is that you can use it up to 35 pounds! And it's really comfortable - both my boys had many naps on my back that way.
I occasionally still use the Ergo, but now that my youngest wants to be picked up, put down, picked up, put down, picked up, put down, I find that a hip carrier is better for that. Infantino makes one, it's basically like a fanny pack with a big hard top to sit on, and an optional shoulder strap. Good for trips to the zoo and such.
And Zolowear has the MOST BEAUTIFUL baby slings EVER! Although it sounds like you already have that one covered.