We have had both the steel ramp and plastic ramp types. My only issue with either is once you clear the outside step, you still have the inside step(at least on the motorhome, I have two inside steps.) I could and did at times extend the ramp up all three steps(one out and two in) but then the incline was quite a bit.
All in all, most times one of us had to help the kid/kids in or out for it to work so I kind of gave up on it. Obviously you had to have the door open to fully utilize it also. Another thing to consider is that the ramp becomes very slippery in wet weather or when your shoes are damp....can be quite dangerous(don't ask how I know). We just lift the two other "small" kids in and out, our 13 year old's.