For my company, they used bottom-up estimation. As they like everything as much accurate as it could be based on analysis and facts. However, there is always some exception based on the volume of the project and what is the profit margin. If I was a PM role, I would prefer bottom-up estimate as most of us do. I think it delays the start of the project, but it could save a lot of money and time. It is considered as risk management to the project and helps for better planning when it’s based on studies and analysis, not on estimated.