While there is a point to getting the strongest stands you can afford, getting too large a ones has its problems as well. I have a pair rated I think at 2 tonnes and a pair rated at 4 tonnes each - and the larger ones have two problems - they only just go low enough to get under the axle housing, and if used on the front the base is so wide that you can't turn the wheels full lock when they are under the best spots just inboard of the ball housing.
Worth noting is that most stands are only designed for their rated load when on a level, hard surface, and you should if possible avoid using them where soft or uneven ground could lead to them tipping over. For that matter, except in an emergency, you should never even jack a vehicle except on level ground - and you do carry a jacking plate for soft surfaces don't you?
John

