Assuming you still provide the same DLI, shoulnd't matter much.
Maybe there are some slight differences based on the rate of application (umol/s)? but overall yield would still be the same. some consideration will depend on local context.. is heat an issue while running 12/12? that's a reason to give the same DLI over more hours, for example.
costs will be 99.5% the same as far as the light is concerned with equal DLI comparisons. You might achieve slightly higher efficacy at the diode with more hours, less intense light per second, but could aslo lose some of that gain from drivers running at lower loads -- drivers are usually most efficient at full load and some do poorly as quickly as 60-70%, while some do fine down to 50%. Just depends on the model.. So, the actual gain might be a slight loss, lol.. can't assume and either way the difference will be tiny.
If either schedule in anyway makes it convenient for you or better jives with power output of light etc etc.. go for it.. use 14/10, 15/9 whatever you want. Provide the same 'max' DLI for your environment and it's going to come out the same. Oh, some people get cheaper rates during certain hours of the day from utility company -- good reason to 'fit' it in.