I have had both of these lights at the same time in the past and after about 3 hours of scanning we have notinced a difference in the weight of the 170 over the 140. The 170 will be the brighter of the two lights and it will have a overall bigger scanning pattern, but it is the heavier of the two. Sometimes having a light with a bigger concentrated beam, not the halo, but the concentrated part just to give you a little more tolerance when looking for eyes. There are pros and cons for both, which is why we have swithed to the magnalights for several different reasons. They have a light that size wise and weight wize is in between the 140 and 170. If you need any info on the lights we use, there is a link on my site you can check them out. I have had every lightforce made just about and we have been more satisfied all around with the magnalight.