You might get more replies in the Babywearing section here. Babywearer.com is also an awesome place to get lots of opinions on both those very popular carriers.
I am a certified instructor & have hundreds of hours of wearing experience. I was a 10/12 pre-kids, a 14/16 with dd1 but am now an 18/20 (cursing outloud right now). And my belly is carrying much of that weight. All that said, I don't like the Ergo. I felt like it sat weird on my belly & pushed my pants down.
If you can, I would consider a SSC made by a stay at home Mom where you can have it actually made plus size. It will dramatically improve your comfort level. The FSOT board at babywearer.com might have used ones & you might get lucky & score a Kanga XT or a Kinderpack in Plus Size. (honestly-the best 2 SSC carriers I have ever worn) They both have long wait lists for new, but used ones are often around.
My other suggestion would be going with a Babyhawk Oh Snap. It is very adjustable & also can be ordered with XL straps which gives you even more flexibility.
Feel free to PM me. Not sure where you are in NY but Metro Minis in NYC has a great selection you can try in person. And if you want to take a drive to NJ, you can try out my carriers to see how they fit/feel :)
Ooops-just realized your baby isn't here yet...the Kanga XT will be too big right now-but the Kanga J would work froggy leg. My Kinderpack is her newer infant design so the bottom cinches so a baby can have legs out-but I found my girls prefer to be froggied anyway. I also love MTs or half buckles for the 1st year...and MTs are very adjustable since it's all straps/no buckles.