Hi Dianne,
Thank you for the question. It is a good one.

Both have their pros and cons.

NING Pro:-
– Low maintenance, less worries about updating
– Less cost for smaller communities
– Has good set of features
– probably better security as their code is closed
– seamless integration between the features they provide

NING Cons:-
– Lack of flexibility. If you need any feature outside of their defaults, it is not feasible
– Plan limitations on storage/number of users
– Limited customizations(themes available via their site)
– Leaves a lot to be desired

Let us see the pros and cons of using WordPress as community platform:-

Pros:-
– Infinite flexibility:- You can extend the community as much as you need.
– Huge Eco system:- You get benefit from the huge eco system as well as developer availability

Cons:-
– Lack of the features available with current community plugins
– A lot of effort needed to create seamless experience
– High maintenance cost & effort:- When using multiple plugins, the whole platform becomes brittle as anyone of them can break the whole site.

The main problem with community plugins with WordPress is you need to devote a lot of time developing/managing a community software than you put on Growing your community/idea.

If you can hire a developer, then I will definately recommend going with WordPress dues to flexibility. If you have a smaller community and your needed feature set is matched by any of the hosted solutions(there are many other than NING), you can go with them.

PS:- If you stick with WordPress this year, we are hoping to solve the frustrating experience users have while creating community with WordPress. Expect a solution by September-October this year.

Regards
Brajesh