I rushed my answer before, cos both my kids started crying halfway through. :P

For ease of use, I can't go past my Pikkolo (which is a SSC, soft structured carrier). Ergos fall into this category too, but personally I like Pikkolos better, because they're more easily used with a newborn. Bub can be worn on your front and older bub can be worn on your back, easy! In the Pikkolo, they can also forward face out, like the Baby Bjorns (but with more support/comfort).

I also find my BabyHawk Mei Tai really easy and versatile, the straps provide really good support, and while at first I found it a little tricky (keeping in mind I'm super unco), now I actually find tying the MT heaps easier than fiddling with strap settings.

Both my boys as newborns hated the Ring Sling and Pouch, but I've found them super handy for a hip carry as bub gets bigger, so I can carry them on my hip on short trips and still have my hands free!

Another style is a wrap, you've probably heard of the hug-a-bub, a stretchy wrap for younger ones, and then you can get firmer wraps for all ages. Apparently these are definitely the most versatile, you can carry bub in any position you want with heaps of support, but there's a huge learning curve. I haven't got a wrap.

Something to remember is that if you're having trouble with any style of carrier, You Tube has heaps of tutorials, it's really handy like that!

Anyway, just wanted to share some knowledge about carriers, cos there are pros and cons to all of them, just like with prams. Carriers are definitely more portable, I'll chuck a carrier in a bag if I take my eldest to the park, if he gets too tired, I'll wear him home! If you go on an outing, like to a market or zoo, carriers can be useful there too, each adult can carry a child, you can squeeze past people in a crowd and the child can see everything (I sometimes wear my nosy eldest while cooking, he bugs me and wants to know what's going on).

I've got nothing against prams, I'm very open to getting the second part of my P&T pram when I need it, but I'm all for options, and I think a good carrier or two can make life heaps easier in many situations.