Google navigation had a major upgrade recently. The traffic info is much more detailed now - I'd say on par with Tomtom. It seems to cover a much greater proportion of roads than before. Tomtom seems to get more timely trunk road closure info from Highways England but its closure data off the strategic road network is a bit hit and miss. Google's now including it's own temporary clousres and Waze info, meaning it's sometimes better than Tomtom once you get away from the trunk roads.. The two are trading blows, rather than Tomtom being the clear leader - as it has been for the last few years.
I'm currently testing a few apps at the moment. Switching between Google, Route 66, Tomtom Go, and Magic Earth (basically R66 with OpenStreetMap instead of Tomtom Maps - both R66 and Magic Earth use Tomtom Traffic info).
TBC but I think Tomtom Go is still the best for quickly adjusting the route with changing traffic conditions, then Route 66 / Magic Earth and then Google. Route 66 is probably best for initial route planning. Magic Earth's default routes aren't as good as Route 66 because the maps lack real data on historic traffic (Tomtom and Google maps both include average speed for time of day and day of the week). It remains to be seen whether Google can find ways around some of the typical traffic on my commute in the way that TT and Route 66 can. Google's routing algorithm seems to be more basic than TT / Route 66. I'm testing them all at the moment to see if a clear winner emerges.
Google's recent traffic upgrade is a major step forward. It's perhaps the first time I've ever known them to be competitive with Tomtom for road coverage. I think Tomtom and Route 66 still have the edge in terms of routing algorithm but it's pretty close.
In terms of up-to-date mapping Google is the clear leader. Tomtom's updates are quarterly and Route 66 seems to be twice a year. Tomtom are due to upgrade to 'realtime' maps in NDS format (which allows incremental changes rather than full downloads) at some point but I think it's some way off for the Tomtom Go navigation app. The 'realtime' maps are already live in Tomtom's MyDrive app but that's just a route planner not a navigation app.
I'm going run these apps in parallel for the time being to observe the differences. Based purely on capacity for avoiding traffic on a commute, Google's now within shooting distance of taking out my recommendation for paid navigation apps. If that happens, it will be the first time since Tomtom launched on Android back in 2012.
Edit: No sooner had I posted the above when Magic Earth removed the ability to subscribe to TomTom Traffic. Users that already subscribed may continue to use it for the duration of their subscription.