WooCommerce Registration or BuddyPress Registration?

I am building a WPMU social niche site with the latest versions of WordPress, BuddyPress and WooCommerce.

I’ve been using BuddyPress for my user registrations but I’ve been told that it is best to use WooCommerce for registrations. So far I haven’t developed any products or sold anything as I’m just getting the site started but I do have almost 100 users registered and I don’t want to make them re-register.

Is is necessary to use the WooCommerce registration or will WC work with BP’s user accounts?

Are there any plugins I would need to make this happen?

I’ve also been told that I should have BP on my main site and WC on a child site. Right now I have WC on the main and BP on a child. Any thoughts on this?

Basically I’m just looking for some direction so I can fix this now rather than later (if it needs to be fixed).

Any help is greatly appreciated!

http://wordpress.org/extend/plugins/woocommerce/