Personal preference. 10,000K is whiter, 14,000K has a bit more blue in it.
If you look at specific bulbs, generally the 10,000K bulb will have more PAR (produces more usable light). It's not a rule though, some 14,000K bulb have more PAR than some 10,000K bulbs and some bulbs work better on certain ballasts so you have to research the bulbs individually. Dr. Sanjay Joshi has done a lot of research in this area if you want to Google his name.