Best forum software for new business related forum/network

I'm thinking of setting up a business related forum/SN and was wondering if anyone has any advice on which forum software to use?

My plan was to go with WP+BuddyPress, and just use the group forums options, but after looking into it it seems that a more dedicated forum software package might be a better choice.

I've used phpBB3 in the past and each time have had the forum completely hacked with spam to the point where I just gave up on it (even with various security measures) so I'm very reluctant to use phpBB.

I'm a big fan of WP, so bbPress looks good but I'm thinking maybe a more pro forum package such as IPB might be a good way to go? I like the look of IPB but it's $175, and not obviously based on WP.

As for my actual site, I like the idea of a private members only section, and perhaps even allow for some kind of paid member ship, which I'm not sure the free forum options offer. I want to be able to customise the look somewhat and not have it look like all the other 1000s of forums out there (or is that not that important?). It has to be responsive to look good on mobile. Also obviously anti-spam measures are very important.

I keep reading good things about XenForo as well.

Thanks for any advice.