Whichever you end up buying - a point to consider - if you have to roll it across gravel or uneven pavement either at home or where you usually go to quilt/sew, small wheels do not do well on gravel.
If this isn't a factor, then wheel size doesn't matter.
I do use the seatbelt to fasten my machine in if I'm putting it in the back seat as if there is an accident, they can become a lethal projectile.
Enjoy!