Are the Visual Magnitudes of bright stars wrong?

I was searching some bright stars, when I did find differences (0.2mag on Arcturus) of what Stellarium (0.13.2) was saying and what Wikipedia (using the Bright Star Cataloque) says.
Stellarium uses NOMAD and Tycho-2 I think.
I was wondering, what the diffrenent catalogues say compared to stellarium.

Search using
  http://vizier.cfa.harvard.edu/viz-bin/VizieR?-source=I/297
  entering name + 1 arcsec and choose the 1 and only star in table
take Vmag NOMAD (Visual Magnitude) (Origin of Vmag is Tycho-2 ;-)
  for Tycho-2 using Link on page
take Vmag Tycho-2 (Magnitude in Johnson V (H5))

For Bright Star cataloque (wikipedia is using this):
  http://www.alcyone.de/search_in_bsc.html

Some bright stars:
Name Stellarium Vmag NOMAD Vmag Tycho-2 Vmag Bright Star Cat
Sirius -1.45 -1.44 -1.44 -1.46
Canopus -0.65 -0.62 -0.62 -0.72
Vega 0.0 0.094 0.03 0.03
Alpha Centauri A 0.1 0.149 -0.01 -0,01
Capella 0.05 0.259 0.08 0.08
Arcturus 0.15 0.175 -0.05 -0.04
Rigel 0.15 0.280 0.18 0.12

Is a difference of 0.2 mag normal and acceptable?
How old are the data in Stellarium and can they be updated to newer ones?