Get the hub first. I just moved my Aeon v1 HEMs to a second hub. Should have done that a long time ago. I no longer have slowdowns on the main hub, and at the database maintenance time I get just under a 1 second delay until about 2:30 or so. After that, normal speed. Now on the other hub, which only has the HEMs (which admittedly are polling very frequently), I do get a slowdown after two days. No problem though, I'll just set that hub to auto reboot daily. Problem solved.
I want to urge anyone that is considering a hub, a second or third, etc hub, to buy the hub before you purchase other devices. First, it is most often the easiest and most cost effective way to solve the problem of old Z-Wave devices that are bringing everything else down, and secondly please don't forget that Hubitat is a small business. In times like these, they need our support more than big companies like GE and Samsung do. They only sell hubs, so please support them by adding hubs when you need them.
For those of you considering Hubitat, please know that you are firstly making and excellent choice. It doesn't take long on the community forum to know that it's a very helpful community, and you will get lots of support from the company and the forum members (just be calm and polite please). Second, please consider that not only are you making a good choice, but you're supporting a small company, rather than just increasing the already enormous cash flow of major corporations. 
