Hm, if I could only have three carriers forever I'd take a size 5 woven for extended wear times, a size 2 woven for medium-length wearing outside the house, and a ringsling for quick ups and downs.
I did like the Boba/Sleepy wrap for the early weeks (like the Moby but stretchier) but it doesn't last very long. I see a lot of people find them a pain to get on/off - personally I just used to tie it on once in the morning and pop the baby in and out all day. I've heard this is easier to do with the Sleepy because of the extra stretch but the tradeoff is it is even more time-limited than the Moby.
The RS and wovens are truly good from birth to big-kid.
I have one SSC but don't like it and never use it.