I have used both for over ten years and apart from the initial weight recovery I gained no weight.
Lack of insulin can lead to weight loss - some type 1 deliberately stop taking insulin for this; it is called diabulimia and is incredibly dangerous. This is the body reacting to the high BG by burning muscle (I think) instead of carbs.
Insulin helps get one's BG under control and reverses this toxic weight loss.
To my understanding insulin does not cause weight gain despite the myth. If it did, every type 1 would be overweight as we have no choice but to take it.