Merriam-Webster lists as one of the verb senses of spur:
to incite to action or accelerated growth or development: stimulate
And for spark:
(1) to set off in a burst of activity: activate.
(2) to stir to activity: incite
The use of "stimulate" as a synonym for "spur" implies that something already exists to be stimulated, whereas "spark" seems like it can be used either as an act of creation or of stimulation.
So if you're thinking about discussions that already existed, "spurred" could be a good choice (or possibly "spurred on"). BUt if the conversations did not yet exist, then "sparked" might be the better choice.
Interestingly, both words are verb forms of nouns. The noun "spark" is something that comes into existence through various means, while a "spur" is an object used to make a horse go faster. "Spur" requires the horse already exist, but "spark" can just originate.
I think what it comes down to is whether or not the discussions already existed.