Is that a Vodafone-exclusive CityFibre area? Reports are that the access network is great but Vodafone's core is awful and they run it too hot still. If Zen can serve you then I'd try and get that.
https://www.thinkbroadband.com/news...ch-services-over-cityfibre-network-in-january
I guess if they're running it too hot, the question is: how hot? If a user on the 500meg service is getting 'only' 200mbit but reliably.. that's possibly still better than a flickering 52mbit FTTC connection.
Of course, keep an eye out and migrate when possible - if the network in your street has ample capacity but that's being squandered by the Vodafone core network then yes, off to Zen you pop as soon as it's possible!
Regarding the speed choice: 500 should be more than ample for most households. I suspect that the fastest 'right now' speed requirement is for game streaming services (Stadia, geforce now) which can use up to 50mbit. So if you're running a few of those then you might well benefit from the speed. Other than that, the extra from 500-->900 would only serve to help you download files quicker. This is certainly useful when installing new games etc. Frustratingly though, if you're installing a big patch for a very popular game, there can be (again) contention elsewhere: I'm on a 150mbit service from Hyperoptic and some of the larger Warzone patches were crawling along at a glacial pace while everything else was zippy. Friends on Sky, BT, and Virgin all experienced the same, so it was clear that the servers hosting the updates were getting a kicking rather than it being a limitation of any of our ISPs.
- I do like to rub it in with you all on discord... Internet talk you say?....
