Different systems and how each system is set up (windowing-averaging etc) will determine how much "other" signals contribute to what you are seeing on the screen.
Windowing: each software has its own scheme, yielding different results. You could argue which is "best", but that's a dead end.
Fun fact: I wasn't there, but I got it first hand from a participant. About four years ago, SMPTE hosted a measurement software comparison session. Same mic, same inputs, etc. Unwindowed responses matched perfectly, which is not surprising. It's simple math to do the DFT and well defined. Same sampling rate and same FFT should yield the same data.
Then, using windowing, they got five different magnitude responses from the five participants.
SIM 48 PPO
Smaart MTW
Systune TFC
and two others
Think about that one for a while......