Let's start with a complete cop out and say ideally you should visit both Banff and Jasper because the drive between these two Rocky Mountain towns along the Columbia Icefields is one of the most beautiful in the world.
But whether you can fit both into your itinerary or not, understanding the differences between Jasper and Banff is important for your planning and getting the experience you want.
In a nutshell, Banff is a ramped-up Jasper with more of everything except natural beauty and wildlife -- which they both have an abundance.
Banff is busy and touristy. Jasper is smaller and laid back.
Basically, many of the advantages for each town could also be considered disadvantages; it just depends on what you're looking for.
Banff Is Easier to Get To
Banff is a 2-hour drive from the Calgary International Airport, which even offers an airport shuttle.
Jasper is a 4-hour drive from the Edmonton International Airport and 5½ hours from Calgary.
Of course, the fact that Jasper is that much farther north and away from Calgary has its benefits if you are looking for a more remote place with fewer tourists. Banff tends to be chock full of tour buses from Calgary.
Jasper Has a VIA Rail Stop
Jasper is one of the stops on the VIA Rail route. The "Canadian," VIA Rail's cross country train, makes its way through Jasper en route to Vancouver or east towards Toronto once or twice per week, depending on the season.
Taking VIA Rail in or out of Jasper is a great addition to any Canadian itinerary. You can sit back and take in the Rockies from the special second-floor glass-domed observation car.
Flying between Jasper and Vancouver may be faster and possibly less expensive, but there is no better way to appreciate the Rocky Mountains than to be in the midst of them. Plus, your VIA Rail ticket saves on a night of accommodation and depending on your package, meals.
Banff Has More and Better Ski Hills
Banff is an ideal launching pad for exploring the big three local ski hills, which are some of the best in the country. A Tri-Area Lift Ticket gives access to the slopes at Norquay, Sunshine, and Lake Louise.
Jasper has the lesser known but much loved Marmot Basin. It is generally not as crowded as the hills closer to Banff but does have 86 named runs on 3,000 vertical feet of drop, a lift capacity of close to 12,000 skiers per hour on eight lifts, and a ski season that generally runs from late November to late April/early May.
Many Jasper Attractions Close in Winter
Because Banff is such a tourist draw year-round, its attractions can stay manned and open from high to shoulder to low season. The gondola, for example, is open year-round, whereas the Jasper SkyTram closes between mid-October and April. This is also true for the Miette Hot Springs in Jasper National Park whereas the Banff Upper Hot Springs remain open at reduced hours through the winter months.
Jasper Is More Remote and Less Busy
Many locals will say that Jasper is the way Banff used to be: Small (at a population of 4,500, Jasper is about half the size of Banff) and laid back. You are more likely to encounter locals in Jasper, whereas in Banff, much of your contact will be with seasonal workers from Australia or Ontario.
For many, the crowds in Banff - especially in the summer - are overwhelming and they are willing to make the added effort to move on to Jasper.
Banff Is Easier to Visit on a Whim
Because Banff is relatively close to Calgary and has the infrastructure to accommodate a wealth of people, it can be pretty easy to get in and out in a day with little planning. In addition, Banff has outlying areas such as Canmore, that can handle accommodation overflow.
You are well advised to plan a visit to Jasper, including booking accommodations and a tour operator.