I think it's pretty much a given PS4 will take July, August, and September, cleanly. Starting from October things get a little iffy with Super Mario Party and Forza Horizon 4 launching in those months. Then in November there is Pokemon for Switch, but Xbox/PS4 will have crazy BF deals, so that remains to be seen....
Bet with Intrinsic:
The Switch will outsell 3DS (based on VGchartz numbers), according to me, while Intrinsic thinks the opposite will hold true. One month avatar control for the loser's avatar.