I've sat inside Boeing and Airbus (intend to take the full course in the future, when I find some free time and for general love of aviation). The controls are completely different. Even if you sat multiple times inside Boeing and then sit inside Airbus you will need a lot of time to get accustomed. Even if you put aside visual differences and that in Airbus you had a lot more electronics compared to Boeing then you have joystick and yoke - the feel very very different. You set up course,autopilot, flight envelope is again different. Windshield and visibility is different, tyres, fuselage length, fuel capacity, you have to take into consideration prior to landing fuel, runway length, number of passengers, load, wind, visibility, clear traffic.
Besides having ILS doesn't mean that it's operational at 100% everytime. You have mainenance cycles, technical issues you are not guaranteed perfect conditions. Also even if you have ILS places like Innsbruck or Madeira you are a push of a button away from ending in tatters. Hell even London is hard to land for some commercial pilots depending on conditions, let alone at a smaller airport.
Let me put it this way even if I know Airbus, even had some flight hours, gone through simulators and all and suddenly appear in Boeing cockpit with zero knowledge about that deck I won't feel comfortable at all landing that plane and there is a big big chance of cocking up something, especially under pressure.