Frank,
I had the exact same experience with the yellow leaves on my seedlings running under 6500k lights. They were slower to grow, didn't handle any change in temps or lighting well at all, and just didn't appear to thrive. I decided to give the other lights a try.
The first picture here is from October so roughly five months ago when I pulled my seedlings from under 6500k lights and then put them under the UVB, 420nm, and 460nm bulbs and the second picture is from yesterday. You can certainly appreciate the difference, I also feed quite heavily.
Most of these seedlings were planted from May-Aug so you can see the growth during that time frame. You can also see the just how yellowed they were vs. how green they currently are.
I have found the cost on the front side of course being different than the standard 6500k bulbs but this is my hobby and much cheaper than building hot rods or something.