I was tempted to get the BT Whole Home system, before I tried the M9. The system does seem to have great reviews but my concern was lots of reviews on drop outs from Sonos users, and terrible support and corrupt firmware updates, but lots of great reviews. Just never been a fan of anything i have had from BT in the past.
As in the Eero's aren't great - well I have read nothing but great reviews from forums, users, Reddit posts, Sonos forums etc (and now myself as a user) and all more or less saying this system is one of the most stable mesh systems on the market. I will admit, the speed upstairs was 380mb + on my TP-link, but the drop outs, sonos issues etc were very very bad. But since reading and talking to many people who are on Virgin and have Eero, it was worth trying it, and so far its been the most internet I have ever used. I must admit, they are a bit pricey vs the BT and others, but they work!! and their support and firmware updates they are listening to their customers with updates and design etc. Just wish Virgin did! Im again if Virgin did a hub that actually gave off great wifi! and a small Mesh device to plug in an upstairs room to expand their great wifi, that would be great.
The system I have is the Eero Pro.