What determines the size of the .vsp file generated by the Visual Studio profiler?

Question

C++ / C#

Hello.
At work, for the sake of interest, I launched a profiler, so it generated a ~ 2GB file in 30 seconds of the program, and my colleague generally under 6GB. A number of questions arose:
1. What determines the size of a vsp file (in particular, does Release/Debug modes and plug-in libraries affect it?
2. Is the studio's default profiler often used at all?
3. How much should one trust profiling data?
Thanks in advance!
PS: Visual Studio 2008, Win7 x64 Projects used Qt 4.7.