2 different sets of downlights off the same switch. How to wire?
Ecnerwal make an excellent statement; doesn't matter. 

I've got 25 years with the power company designing underground systems for high rise buildings, residential subdivisions and downtown areas. We hate radial feeds because if you have a problem, everyone's out. So I'd be running both sets to the switch. If something goes wrong with a section, you can disconnect that section from the switch and power up the other set so you have lights to fix the problem. (I know, I'm being ridiculous).