Nikon 24-120mm f/4 vs. Tamron 28-75mm - My Quick test (on D600)

That is a sharp copy of the Tamron! If you do a lot if indoor portraits, particularly if handheld, the lack of VC maybe something to think about. But then it is a F2.8 lens.......so you got one stop on the Nikon.

Try taking 40-50 shots at slower shutters <1/15s at various FLs and see which lens gives you the most % of sharp shots.