With the same 16g main, the 17g cross (instead of 16g) should (usually) be softer. Softer string bed should translate to a bit more pop and spin, at the expense of some durability and potentially poorer tension maintenance.
Personally, one of my go to setups for customers is 17g poly mains and 16g nylon synthetic gut crosses. This usually softens up the poly string a bit - which most recreational players benefit more from (than having a stiffer, more control oriented thicker gauge poly main).
Bottom line, there’s nothing wrong with mixing gauges between mains and crosses. Sometimes it can be advantageous. Other times maybe not so much. Only way to know is to experiment.