I've been playing with home automation since the X10 was popular.
I use the Alexa, the Wink, Chamberline Garage Door opener, Harmony Hub, Nest Thermostat and smoke detectors and various types of light switches and plugs. Whether you you use Google or Alexa is a personal choice. They both function similarly. They allow for vocal integration to the automation system. The Wink or Smartthings are nothing more then hubs that interact with the usage of a smart phone to control the various devices such as light switches if a vocal hub is not introduced. No one can predict the future longevity of any device such as a hub (wink vs Smartthings). I personally do not like to control devices via a smart phone, as I find it too cumbersome. Once I added the Alexa the whole system ran as smooth as silk.
As for switches and bulbs. If possible strive to replace a switch. If economics is an issue, sometimes a wifi bulb is cheaper then a switch. The downside to a bulb is that someone can come along and turn off the switch and if left off long enough can cause the hub to drop the device thereby needing the device to be reset within the hub. My overall collection of switches are the Lutron Caseta and a couple of Levitons. The Lutrons are a two wire based switch that does not require neutral connection. The vast majority of my lighting works great with these but certain light fixtures do not. Some LED fixtures require a neutral connection and in the situations that I have experienced, without the neutral connection the light has an oscillating or strobing effect; so the Leviton fixed this.
In my dealings with the help desk with Wink, they are excellent and knowledgeable. I choose the Wink as I found it to meet all of my needs. In many cases many devices will offer a hub but this is only necessary if one does not have a primary hub such a Wink or Smartthings.
You may desire a form of automation that is not out right controllable. The IFTTT is great in these situations, such as my garage door opener. The door opener works great with a smart phone but is not as straight forward with Alexa. When I initiated the IFTTT option, it now works via voice commands.
In a nutshell, this is more of a personal choice issue. If I can give you a word of advice, that would be to check out what it is you want to automate. Go onto You Tube and see what others have done and make a list. If you have a spouse, talk it over with them and see what they would like as well. In my case my wife wanted to control the stereo system via voice command hence the Harmony Hub. Next see who can source the equipment needed. Is the suppliers local? (In my case Best Buy, Home Depot and Lowes offer the basic need for home automation.) Is there a difference in cost from one to the other? Always check the packaging to assure that the product you are buying is compatible with the system you have chosen.
This is something that is fun to do and the possibilities can be almost endless. As for me, my next stage is to have an automated main water shut off in the case of a major water leak.
If you have any other questions just ask and good luck.