Hello Sir,
I am Nisar, experienced in Web development. My recommendation for you as i had similar kind of experience in past and based on that i am going to share information.
1. Use any of the 2 social networking tools you provided, dont go for custom , you will waste lots of money and time
2. if you rely on these 2 platforms cloud based service then thats ok, but they charge monthly fee and all that which is not good
so best thing is to buy the software from them but add on your own domain+hosting , so in that way you will have to spend only once on some freelancer etc.
i hope you understand my points. take care. thanks