If looking at mirrorless camera, there are a few that are excellent,
1) Sony - NEX and A55, A33
2) Samsung - NX system
3) Olympus - PEN series (m4/3)
4) Panasonic - G series and GH series
And true, Nikon's sensor are make by Sony, but a camera is not only about the sensor, there are other things at play too... having said that Sony make wonderful cameras (absolutely loved the A55 - after having have a brief hands-on).
So my advise, like many others here, TS was to ask his friend to go down to the stores and test out all these cameras... or any that was within his friend's budget and see which one he/she like best before committing to buy... instead of asking for advises on which brand is a better buy, because like what I have stated before,
"What works for me, might not work for you."