So I have programmed everything into Google Home and used it for awhile. Like everything else, there are pros and cons but I will say now that with Google Home, the pros far outweigh the cons for me BUT read on, I still use and need both systems!!! I also use multiple devices in a room, one has 10 devices. I have seen many people use only up to 2 devices per group, it gets too complicated for them to use and set up... you have to be organized and consistent with your naming conventions otherwise it will be mayhem especially in Alexa.
Pros - Google command structure are so much better than Alexa especially with several items in the same group... with a few exceptions. Also, it is not prone to near as many errors as Alexa such as turning on the wrong item or even turning on items in two different groups at the same time. Also, the issue with mixing up OFF and ON is nonexistent in Google. Alexa also ignores a lot of commands and have to be repeated. Once a device is paired, Google will see it. Alexa needs to register with the 3rd party first.
Cons - Google does not use 3rd party motion sensors/switches working through hubs in Routines although it recognizes them as devices. I still have to rely on Alexa to do that BUT Alexa is known to drop these connections every now and then. Google does not have a lot of free stuff so I still rely on Alexa for that. I also spent a fair bit of money wetting up the Alexa quad pseudo sound system so unless I eventually get rid of Alexa, I will keep that. Google has a very annoying feature whereas it groups all lights together in a Group and turns them all on/off together regardless if you command just one. There is a workaround for this though by making sure the device is not in any way programmed to be a light of any kind (smart bulbs must be) and don't use the word "light" in the description. it seems Google will eventually search out and gather that item into its "light" grouping. Smart bulbs have to be kept out of any grouping at all to avoid this issue. I found that Google has a few commands that it just doesn't like and have to change the command to suit and change this for all devices of the type so I am consistent. Google doesn't have a whisper mode which nice very late at night but it works erratically and Alexa ends up screaming back when you don't want it too. Typical of many Alexa special features, sometimes they work, sometimes they don't.