I have the Whole Home, I paid around £180 and this was a one off fee for 3x devices that I have taken with me from Virgin to Sky.
I believe the Complete is a rental package.
I think other than different firmware they are in short the same device but I cannot confirm this.
If you wanted the best speed possible hardwire all the devices this would give maximum speed and will work the best. I would of found this useful when I was with Virgin, My first hub would pull in 380mb on wifi, the other two would be around 200mb on wifi. Since moving to a 80/20 package with Sky they all get the same max speed. Although my devices are rather close together meaning they can share this speed, if one of my hubs had a low signal the speed would be much reduced.
IT Tech for 9 years in the Private and Public Sector, recently giving it up for a totally different career change.