Obviously, you will need a certain kind of tire depending on how you use your vehicle. Due to this, a 235 tire might not be better than a 225 tire, or vice versa, but depending on your situation, one tire might serve you better than the other.
Since a 235 tire is a wider tire, it allows for more stability on the road while accelerating. This is especially useful for larger vehicles, like Land Rovers.
The weight difference between the two tire sizes is negligible. The weight of the tires should not factor into your decision.
If considering gas mileage, you'll want a tire with less rolling resistance. The 225, being thinner, has less rolling resistance than the 235.
In terms of cars, you'll want to find out how much load it can carry. Cars that can carry a higher load need 235 tires. Cars that need less of a load can have 225 tires or smaller.
If you have a smaller car and want to save on gas, you'll want a 225. If you have a larger vehicle and need more stability, you'll want a 235.
