Traded our '02 Ford CCLB 7.3 for a '13 Ford 6.7 CCLB. Both SRW. There really is no comparison between the two. The '13 is quiet, smooth, better on fuel and has ridiculous power; the same grades that were 3 miles at WOT are now climbed at 70mph in 6th gear (it will drop to 5th if I have to slow and come back up to speed for traffic).
The truck you describe sounds nice, but my gut says the asking price is a bit high for what is essentially as used vehicle. If you don't care about the creature comforts of the Platinum you could likely score a better deal on a brand new Lariat or XLT, with patience of course.
The biggest change between the '14 and '15 IMHO is the improved exhaust/engine braking.
One thing is for sure; these new trucks are expensive to fix if and when something fails outside warranty.