i think its just the photos. the skid is moved back, and the chaincase is 27mm longer. so it shouldnt be any worse than a factory summit x with a 2.5" track i wouldnt think. the inch longer chaincase will makeup for the smaller drivers.
also remember that 174x3" they managed to make it the same weight as the 163x2.5" so perhaps they found the driver size made up for it enough
The attack angle is steeper. They would have to push the skid back to make the clearance for the track, otherwise with the taller track and smaller drivers you'd potentially have the track coming down towards the drivers off the front arm.
The 3" sits higher and flatter just due to the fact there is so much track back there, to keep the balance on the front, you can use longer shocks but it puts excess stress on the steering components without geometry changes. Look at the spindles on the front of the 174 and then on the 163/154, you'll see that they are longer. The front of the sled on the 174 sits higher and this makes the angle steeper.
Will it affect performance? The increased angle will be a small trade off to get the 174" X 3". I don't think most will notice the performance loss, and honestly, most guys will have to tighten up the limiters anyway to keep the front down, so that will help improve the angle a little anyway.