Hi Glenn,
I’ve never tried Peepso or Social Engine, so I@m not speaking from a point of balance. I have tried other dedicated hosted platforms such as Ning though so I do have some wider experience.
I think your issues can be boiled down into two areas: Maintenance, and features.
Any WordPress site, any site for that matter is going to require maintenance the main question is who does that maintenance, how well is it done and how quickly new issues can be resolved.
With a WordPress/BuddyPress installation I’d say that the level of maintenance that you yourself have to do (or pay for) is going to be higher than with peepso. Much depends on what features your add to the basic installation, in my experience in general WP and BP updates are solid and cause few issues, it’s usually the other plugins that can cause issues (prime eample recently was a SiteOrigin Page Builder update that wrecked my front page and they did not fix it for several months).
My expectation with Peepso is that what you sacrifice in the way of variety of options available to you I’d hope that in return the options you do get will be reasonably well integrated with each other and less likely to cause conflicts resulting in feature or site loss that you would need to take a hand in resolving. The downside is if you find there are specific feature you need, or issues that are not getting resolved, you have few alternatives to go to, you may find yourself stuck.
I once had a paid hosted site costing $50 per month which pretty much ground to halt and the provider refused to see the problem. It made me feel pretty helpless and it was the reason I moved to BuddyPress – I figured the money I saved on hosting I could use to fund feature additions to the basic BP setup.
Anyway getting back to the point, so I reckon peepso will be less maintenance but with less features, and this brings me on to the second point – features.
I think it would probably be a good idea to map out exactly which features you want in quite some detail and see how that drives your thoughts. For example you say you want video, would this be you hosting the video files or libraries of YouTube style embeds? Would you need group galleries, user galleries, sitewide gallery etc?
Here’s what I tend to use:
Chat – IfyChat – free version limited to 10 concurrent users but an excellent chat engine
Video/photos/audio – Either MediaPress or rtMedia, rtMedia is more stylish but add-ons are quite expensive.
Groups/xprofiles, activity, friends – BuddyPress.
News areas – probably more general workpress based solutions for this, are you thinking RSS feeds from other sites or internal news (could be done with a simple News category?).
Polls – never really looked at polls, I note there is this – https://themekraft.com/new-plugin-buddypress-polls/ for starters, looks interesting but I’ve not tried it.
Regarding supporting mobile, BP is coming out with a new theme – BP Nouveau, this has options for vertical menus which I think will be a lot more mobile friendly.
The bulk of being mobile friendly comes down to the theme you are using and whilst most are responsive these days I personally find that having a mobile responsive theme is not good enough for phones, what I do is run a second mobile specific theme and use a theme switcher to detect and switch themes.
Another point to bear in mind with BP is that there are a great many plugins that help you choose how your site is going to work, there’s a range of plugins that change the may notifications and email subscriptions work. This is a benefit of BP, but it does also increase the plugin count.