Both the NXT Tour S and DT Solo are softer than Velocity.  Both have yellow.  I'm stil trying to decide if I can see a difference from my few remaining  NXTs (R.I.P.) and DT Solo.  Both tend to stick closer to the fairway and my best way to get a ball to check on the green is to loft it high and hope the roll direction is not downhill. 

There is a fair amount of competition in the high end 2 piece/low end 3 piece ball market ($16-25).  So if Titleist misses the mark for a sizable population that is looking for a ball that is long, checks better than DT Solo, less expensive than NXT Tour S and is yellow, then the free market system will correct this.  Probably not many golfers with driver speeds much over 90 that can't follow a white ball so the Velocity in yellow may not be a big market.

Without directly picking on geezers, the yellow balls are directed at this age group.  Not an accident that they are starting with their softer feel balls.  If you can work your shots a little, the NXT Tour is a different option from DT Solo.  Spend a round comparing NXT (R.I.P.), DT Solo, another yellow ball that asks if you want to play from the fairway or OOB, and a metallic-named ball with 6 sided dimples.  The NXT and Solo stayed straighter than the yellow ball with 6 sided dimples.  The fairway yellow ball was a little more prone to sidespin and is a 25% premium over the DT cost.  The distance with the 3 two piece balls were all pretty close.

Unless someone with a driver speed under 85 mph has done a comparison with Velocity and DT Solo to define a difference or there is a yellow option in Velocity in 2013, DT Solo will be my NXT replacement.  There might be some other soft compression 2 piece balls for less money, but NXT was my go-to if I was not hitting straight enough and I now have confidence that the DT won't emphasize my faults. Playing a course with narrow fairways and marshlands for the rough has taught me not try to use a ball that can sidespin as fast as it can backspin.