I've brought down two different ones. When my oldest was nine months, and then again when my middle was five months old, I used my Maya Wrap (sling). When the younger one was a little older, I used my Babyhawk (mei tei).
Benefits to the sling:
He could face out better, yet when he was sleepy he could tuck into it nicely. It is lighter weight fabric (and that's why I'm defnitely taking it again in June).
Cons to the sling:
At that age, I felt like it was really stable, but always had a hand on him just in case. My back did start to hurt in less time than with the mei tei.
Benefits to the mei tei:
Easier to use, IMO. Best for when the baby is calm, ready to nap, or already sleeping. Felt like my hands were both free with this one...it's really stable.
Cons to the mei tei:
If it's warm out, make sure you have a tank top on. You will get hot in it faster as the fabrics tend to be heavier.
I also have a Moby, which I really like. I'm still learning how to use it. It's not likely that I will bring it to WDW, but if I do it will be in place of the sling as it is more similar to that.
My plan is sling in the morning and early afternoon when he's active and it's really hot. And then we we go back to the hotel for a break, I will switch to the mei tei for his sleepier evening time.
www.babyhawk.com
www.mayawrap.com (I think...
)
Good luck with the little one!