confused on car seats

Hannah • 26, Mother to Oliver, Nathan, and Mia. TTC👶💙 💖

Should I be buying an infant seat with 2 bases one for each car? Or a convertible seat (4 to 65 lbs)? The infant seat has the stroller, so idk what I'd use if I got the convertible one. Also, if I got the convertible one, that's means I have to switch it from one car to another since it has no base right? Or buy 2 which is expensive. Idk which option more is cost effective and convenient.