I don't have direct experience with either. What I'm started with is a simple Z-wave bulb and SmartThings Hub controller.
Technically neither of these are "home automation product" per-se. They are more of way to provide voice control to other things, like for example it seems like both support Smarthings for example. Think of these as human head, but head can't move without the body (smarthome hub)
https://www.smartthings.com/products/google-home
https://support.smartthings.com/hc/en-us/articles/205275404-How-to-connect-Amazon-Alexa-with-SmartThings
There are dozens if not more of "smart" home products and solutions and you have to be either careful selecting compatible products or bang your head against the wall try to make it work.
Unfortunately there are no single and easy standart. Do a lot of homework before you dive into that.
Try to figure out which systems you would like to control: Lights, Blinds, Garage, Alarm, A/V, Door Locks, video security or Hvac. You'll have to make sure that each system is compatible with your "smart" hub.
One thing of note is this: Both these voice controllers require internet. Same goes for Smarthings hub - without internet and cloud (I couldn't use management app while Amazon had major outage recently)
Maybe it's just me, but I knew it before, I'd probably look for another smart home controller.
I haven't look into this deep enough to be expert, but I hope this gives you some idea what are you looking at.
p.s: I think I've mentioned Samsung owned product one time too many, but besides my familiarity with it, it also has been selected few times as most versatile hub out there. It's not perfect, but it does the job. If you could program Harmony remote - it's a similar effort level.