The following FAQ, particularly post five, should answer some of your questions (this is a clickable link). The FAQ IS old but still accurate.
To answer your specific questions, Wi-Fi devices typically use 4 to 10 times as much energy as zigbee, and about 5 to 8 times as much as Zwave. But it depends on the specific models, some manufacturers worry a lot more about power efficiency than others.
With regard to repeaters, there are two answers to that. First of all the whole point is that mesh devices repeat for each other. If you have a Z wave light switch in the living room and a zwave light switch in the kitchen, they can repeat for each other. You don’t have to buy special repeating devices. Most people will not have to buy extra Devices just to repeat. See the following FAQ, start with post 11, then go back up to the top and read the whole thread.
The second answer is that because it’s a 360° signal and zwave plus will cover typically around 65 to 70 feet in standard US residential construction, for many homes that’s already enough to cover a home. Certainly an apartment.
So it all comes down to exactly which devices you have and where you are going to place them. There’s no question that Wi-Fi has much better range than zwave, it’s just that for home automation, Just the devices themselves are usually enough to create a mesh that will cover a standard house. See the following FAQ:
From my own point of view, the number one issue with Wi-Fi is that power consumption is too high for battery powered sensors, and I really like battery powered sensors for home automation. 
Both motion sensors and contact sensors can give you a lot of flexibility In adding Home automation. For that matter, there are only a couple of Wi-Fi – enabled smart locks because of the battery usage issue, and most of them get terrible reviews. I would always choose another protocol for a door lock.
And of course the practical limit on the total number of Wi-Fi devices you can have is low enough that many people trying to automate an entire household run into it. I can fix the range issue with mesh very easily, but I can’t fix the router issue without upgrading to commercial grade systems which are way more expensive than the amount I’d save by using WiFi switches.
But each person has to make their own decisions with regard to which protocol or protocols will work best in their own home. If you find Wi-Fi switches that you are happy with, you don’t care about the energy usage differential, and that’s the only Device class you need and you don’t max out your router slots, go for it.