Originally posted by Clavius But in the real world I promised my wife that I wouldn't expand my lens collection any further.
Very understandable. If I could only have ONE of these lenses, the versatility of the 18-135 would probably sway me towards it. I have taken photographs with the 16-50 that I would not have been able to get with the 18-135, but not that many. If low light shooting is something you want to do without flash, the 16-50 will work beautifully. If you don't need the f2.8, stick with the 18-135.
The IQ of the 16-50 is better IMO, but my 18-135 is very good too.