Sony Vegas is not a professional level program, FCP is!!!! you can bet anything vegas does FCP will do better with greater results.
With all due respect, that isn't entirely true. I suppose it really depends on what what the user expects from his NLE package. There are things that Vegas can do that FCP can't do and vice-versa. For example, Vegas natively edits R3D video from the RED One camera (performance of course, varies greatly with the speed of your hardware), while FCP requires a transcode. Vegas is also 64-bit native like Premiere Pro and can utilize more system memory for better performance.
FCP on the other hand supports a much broader range of professional codecs, like DVCPRO and Panasonic P2. Vegas can only support these through third-party plug-ins like Raylight.
Overall as an editor, I've observed that Vegas has been targeting mostly next-gen post-production workflows - and those have primarily been the tapeless varieties like XDCAM, RED, AVCHD, etc. Vegas (and even the newer versions of Premiere Pro) have been executing these workflows quite well. In all honestly, you can't always say the same about FCP. The majority of its solid state format support requires time-consuming transcoding and that will remain a problem until Apple hopefully does something about it in a future version of FCP.
When it comes down to it, Avid, FCP, Premiere, Vegas, etc. are merely tools that all produce professional results with perhaps different ways of getting there. The best advice I can give to the OP is that you'll have to determine what your needs are and which NLE will make that happen for you within your budgetary constraints. Because in the end, it's not only the car that wins the race, it's the driver.
FCP and Avid are the dominating legacy cutting platforms for film and television and a lot of editors find themselves becoming well-versed in one of them or even both. If nothing else, it's easier to collaborate with other trades using the big gun packages.