Boot Camp does not involve emulation at all. Windows on a Mac is just as fast as it would be on a PC. Macs use Intel processors now and thus do not require require emulation as they are essentially a PC inside. You should also look into Parallels Desktop or VMware Fusion that allow you to run Windows alongside Mac OS X. These also do not involve emulation but are not quite as fast as Boot Camp because they are sharing resources between both operating systems. They are also not suitable for any 3D work as they do not support video acceleration.
Since a Mac can run Windows and OS X it allows you to select the best one for the task at hand. Another benefit to 2 operating systems is that if one should become damaged then you have the other as a temporary backup.
I also wanted to mention that Yoho's links comparing Mac vs PC performance were for the old PowerPC Macs and not the current Intel ones. Things in the Mac world have changed a lot in the last 2 years.
To sum things up, like others have said, most engineering software is not available for Macs but Windows can be installed easily and provides the same performance of a PC with the same specs. Most of the engineers I know use the fancy software in the computer labs at school and are mostly using Microsoft Office on their own laptops. And Microsoft Office is available for Mac OS X and it reads files created by Office 2003 or older on Windows.
Almost forgot, the downfall of Windows on a Mac is that you have to buy it separately as it will not come pre-installed like on a PC. This could make it more economical to buy a PC. If you are still considering a Mac even though you will need to install Windows, I would recommend joining the MacRumors.com forum to try to glean more information about Macs so that you can make a more informed decision.