Very interesting I have 100’s of devices from hive lights, TRV’s, ring cameras and door bells etc etc as well but struggle with HomeKit Alexa seems to do a far better job maybe I am doing something wrong then
I have nearly perfect uptime. Siri can be a little sketchy, as people love to drone on and on about, but my trouble with Siri is when she can't hear me well and misinterprets what I said. In the context of HomeKit usage, if she hears me properly, she does the task fine.
Speech recognition is pretty good, but that is an area I hope Apple continuously improves. Especially as requests get more and more complex, as opposed to "Play" and "Stop" and "Next Song" like HomePods were originally kind of designed for.
Really, the only time anything is unavailable is if the battery is out or some device is updating. (Although even that is rare, because the HomePod's never seem to all update at once. So even when my designated home hub HomePod goes offline for an update, one of the others just takes over, and then they trade back and the other one updates.)
I've found having a rock solid WiFi network is critical. And to having as few WiFi smart devices as possible. Most WiFi routers just weren't really designed for tons of tiny low-data-rate devices, that's just not WiFi's best use case. Zigbee and Thread are much, much better for smart devices.
My air conditioners are all WiFi, and there is no way around that. And since each air handler has its own WiFi connection, that's 32 connections right there. Luckily they're all very stable. But that's already a lot, so I generally avoid any other WiFi smart devices when I have the choice.
Thread is basically just the newly revised Zigbee, created by the same people, with some substantial improvements. But still very similar, and still well suited to smart devices like sensors and light switches and outlets and buttons which just need to send a tiny blip of data every once in a while as opposed to WiFi which is designed to continuously transmit dumpster loads of data every millisecond so you can watch your 4k Netflix.
HomePods can be your Thread border router already, so you don't need anything. For Zigbee, a coordinator/hub that has a wired ethernet (or USB) connection is great.
Thread and Zigbee are both mesh networks, so the more devices you have that expand and fill out the mesh, the better and more resilient they are. For Zigbee, which is my primary device type right now, I used Zigbee light switches in every room to control the lights. Since the switches are hardwired to power and therefore signal repeaters, that means every battery powered end-device sensor is no farther away from signal than the light switch in its own room.
If you're well established with Alexa, certainly no reason to change. But HomeKit isn't inherently lacking on the software architecture side of things, so there's no reason to avoid it if someone was picking a system to use.