depending on where your devices are going to be located you cannot just add 2-3 and expect reliable behaviour especially for instance if you try to add edge devices like door or stuff in the garage without a reliable mesh.. both zigbee and zwave require a good mesh. so build out close to the hub first with powered devices to strengthen the mesh before adding batter (non repeating) devices.
Most people don't need two hubs. Exceptions you might know right off the bat:
If you want to use Zigbee bulbs (Sylania/Osram, Cree, Hue, etc., or at least certain generations of these) but also have other Zigbee devices (sensors, switches/dimmers, etc.) that they many of these are known not to play well with, or possibly Xiaomi/Aqara devices for similar reasons
If you have range issues, like a detached garage where you have LAN connectivity but are less likely to get Zigbee or Z-Wave there despite a need for such devices (less likely to happen inside your own residence with enough repeaters, but I guess everyone's house is different)
If you have any chatty S0 Z-Wave devices like the Aeon HEM and don't want to (or can't) tone down its reporting -- and have other Z-Wave devices on the network that might care about this, or maybe a large (50+?) Z-Wave network, though I also wouldn't start with two just for this reason.
As a distant third, if you don't plan on being careful what community apps or drivers you install, maybe you'll want a second hub for those. (I've gotten picker, and it's mostly stuff I've written myself now.) Poorly written apps or drivers might be able to drag down down your hub -- but so can plenty of things you do yourself if you aren't careful with built-in things, either (e.g., nothing is stopping you from writing a periodic rule that triggers every two seconds, but you probably shouldn't).
i wouldnt call 50 large i have more than double that and same zigbee on one hub.. it all depends on your device mix and how you can tone them down.. i am carefull not to have too chatty motion or temp/humidity /power reports or just 20 devices can bring your hub down.
Yes, it will depend on the specifics of your network, and it's why I suggested not consdiering that a reason from the start. But the number wasn't entirely made up; it's based on what staff have noticed with some networks, even though it's well below the theoretical max for (traditional) Z-Wave.
Though I guess I should have mentioned that if you have more than 232 Z-Wave devices, then that's as reason. But I probably wouldn't try that many on one hub anyway, even if you somehow managed to fit that many into your home.
I had good intentions of migrating everything over slowly and methodically to minimize interruption, but once I started moving stuff, I realized that was going to be impossible. After moving the first couple simple things over to Hubitat to get the hang of it, I just went for it and did everything at once. It only took about 2 evenings to get back to about 95%. In the meantime, we just had to turn lights on manually like the cavemen used to do.
Thankfully, my webCoRE pistons moved over Ok, though I did have to edit each one to point to the "new" devices on the Hubitat. I probably had 75 devices and 30 pistons.
Probably not the brand in general, certainly not just that one, and likely a firmware oddity or perhaps hardware limitation on certain devices, but they are known to occasionally "drop" messages that they are supposed to repeat, which can cause hard-to-troubleshoot Zigbee network problems. They behave fine with each other, so the issue is if you mix them with non-bulb devices like (other brands of?) smart plugs, switches/dimmers, sensors, etc.
Just to note, you can turn on the Alexa integration on Hubitat as soon as you start using it. It wouldn't conflict with SmartThings.
And, even better, you can select which devices on Hubitat you want exposed to Alexa (unlike SmartThings, which used to allow you to do this, but for the last 2 years has forced you to expose all your devices).
Migration going smoothly. I only goofed with one switch that was furthest from the hub. Excluding it from ST isn’t working. It might also because it’s an older GE switch and I’ve seen reports that some of them never exclude. I’ll likely just replace it.
The remaining few devices to move are plugs. Then I’ll add/replace some switches that I’ve been meaning to for a while. So far loving the capabilities offered by Hubitat.
I might give that a try when I've finished moving everything. The Switch will have to come out anyway as it is a fan switch running a plain light. At least then if I can exclude it I could redeploy it if needed.