It's a fair question!
As a 28 year cable TV customer (United Artists -> Telewest -> Virgin, maybe some other names I've forgotten!), who finally gave up on it. As someone who has no love for Sky - I hate what Sky Sports has done to sport and the accessibility of sport in the UK. As someone who would love some competition pushing forward TV and stuck by cable through promise after promise over the years. As someone who kept Virgin Broadband and would love to come back to Virgin TV for a genuinely competitive offer:
- The main thing is the content - 4K sport (football and next year F1). 4K movies, on subscription with Sky Cinema and Pay per View. 4K TV drama, limited at the moment, but at least there.
- From a pure tech spec point of view - 12 tuners, not 6 like the 2013 TiVo Roamio. Allowing simultaneous recording of 4 shows, plus live TV on 5 devices (3 TVs and 2 tablets), plus extra tuners to "next gen" the interface (live channel previews for example). I don't think the ability to use more tuners for recording, but then not available for viewing, will benefit many, if any users.
- Mini boxes which can do just about everything the main box can do - watch live TV, recordings, on demand - with no need for anything other than a mains socket - and which TiVo themselves have had for years.
- An interface that is still in development and far from perfect, but just "feels" current, compared to the TiVo. It's genuinely UHD. Live previews are impressive. It is identical (adjusting to screen size) on all devices - main TV, Mini boxes, tablets and phones and at home on them all. It feels a modern interface, for those used to smartphones and tablets. All of this is subjective, I grant you, but it just felt like a breath of fresh air to all my family, coming from TiVo, even after the latest update.
- I hesitate to mention the Sky mesh network, which is genuinely "next-gen", but at the moment maybe a bit too cutting edge and possibly flaky! It is a supposed to build a more reliable home network by interconnecting all Sky devices, using multiple paths, over wifi and by built-in Powerline, for both video streaming and normal WiFi for home devices. Personally, I have it all disabled! My boxes are all connected by Ethernet, which works well with my Virgin broadband

. But there is no question it's aspirations and technology is "pushing the envelope".
Now all of this may be uninteresting to some/a lot of people, and fair enough, but I think it's enough to claim "next-gen" in a way the V6 simply cannot.