Interesting fact: doing a search in the livery section of the in-game Discover menu yields the following:
In the search period 27/3/2019 15:53 to 28/3/2019 21:23, 1364 liveries have been uploaded for the Honda version of the SF19.
Over the same period, only 891 have been made for the Toyota version.
Since you can't cross-use the liveries, fans of custom designs may well be better off with the Honda, as for whatever reason, the internet at large has taken to that version.
Maybe it's for the inevitable deluge of Senna McLaren-Honda designs...