It depends on the term.
If the keyword is short and brandable, something like SolarCo, CloudCo, etc. works well.
If the root word is less brandable, I think "Company" is a better ending.
In the first example FlowerCo.com is a good brand, and FlowerCompany.com is good as well.
The second example I would rather have RealEstateCompany.com by a wide margin.
Brad