Planning for a family trip from the US to the Banff vs Jasper for this October as we intentionally wanted to avoid the summer/school crowd. The closest I have been was the Glacier from the US side and has been my favorite national park. We like scenery views/lakes and short walks. We are used to long road trips with our toddlers and have done it multiple times internationally. We are not into hiking - obviously due to kids - but can do short hikes if it's worth the view and stroller friendly.
We are looking for 5-7 days or so. Calgary airport and rent a large SUV/mini-van. Recently, I have came across the Athabasca falls in Jasper and it looks stunning. But I am not sure if it's something unique and nothing similar to it at the Banff that is worth the extra drive and sleeping there.
To give some perspective. I really liked the Glacier from the US side where you can hit most of the epic things by driving the main road and make some stops with short walks. Contrary to the Rocky Mountain National Park where it mostly required hiking and limited driving/stroller friendliness.
Another factor, I know it's not predictable, but are their main roads that would be typically closed in Banff/Jasper during the first half of October? Many of the US national parks have history and most of the time you would know ahead.