the problem with the standard equipment jacks (scissor jacks) are that they are a PITA to work with, more prone to failing / tipping over / bending
in most cases the bending part is the users fault but - the main problem is that they do not allow for movement which is needed when lifting up a car. so for an emergency tyre change, they're fine but otherwise i stay away from as far as possible..
those things are called a 'widow maker' for a reason
best part about a trolley jack is that it moves in or out accordingly as you lift the car
as Xulfiqar said, I would suggest you to find a good sized used jack.. or otherwise get a good new 3-ton jack, will cost around 10k but will be good for a long time.