Yz 125 or CRF250R which one?

Firstly was your bike a crf150f or a crf15r as if it was the 'f' then either of the choices you mention are going to be a big jump for you. If you have never been on a 2 stroke then it will be a lot harder for you to ride as they are completely difference to a 4 stroke and both bikes are much of a much sixe wise although the 4 stroke is a little heavier. The power delivery on the 250f would be easier to manage than a 2 stroke. So perhaps you need to get some of the facts about both bikes and present them to your parents. Personally for someone who has not come up through the ranks of racing and learnt how to race and ride a 2 stroke I would prefer to put them on a 4 stroke any day.