River Garden is a definite success, a huge improvement over the St Thomas projects and managed by an excellent local company, HRI Properties. They have had some crime issues previously (unfortunately many of our historic areas suffer from social ills) but the management is very responsive and in 2012 installed a private security patrol and closed circuit TV system that rivals or exceeds private security districts (paid through tax assessments in the Garden District, Uptown, Audubon, etc.)
Buyers in River Garden are attracted to low-maintenance and high-quality new construction. Some folks don't like the 'planned' feel of it and prefer the more organic historic areas like the Irish Channel.
It's all good - something for everyone in this area. So overall, I'd say both areas play off of each other to their mutual benefit.
Good luck on your home search!
(Disclosure - I have personally lived in the Irish Channel for over 10 years, walking distance to River Garden and we love it. I have represented HRI at River Garden and represented many loyal buyers and sellers in both neighborhoods)
As such, the changes are dynamic and demand will continue throughout the city.