This depends on your risk tolerance, finances and experience.
A Well-known Franchise offers the benefit of brand recognition, with customer loyalty from the day you open. Their business models, training and systems have already been proven over time, making your chances of success higher. Of course, this can come at a cost, as a well-known brand is likely to have higher initial and investment costs and more limited flexibility.
An Emerging Franchise can often cost less to get started however you'll have to work harder on developing your customer loyalty. This could mean higher marketing costs and a slower initial growth. One of the positives in emerging brands is the great new franchising ideas that are now in the market. Over the past 5 years, the franchising industry has been exploding with new and non-traditional business ideas.
Some emerging brands may still be fine-tuning their business models or systems, while others will have it well set-up. You'll need to know this before you commit. If you're new to franchising, you need to be sure that you'll get enough support.
For an experienced franchise operator, an emerging brand can offer great opportunities. With few established locations, you can get in on the ground floor and use your franchising experience to scale up to multiple units fairly quickly. Just be sure to do your market research around customer demand.
Simply put, if you want stability and have the finances, opt for the established brand. If you're willing to take some risk at a lower cost, you may want to look at emerging brands.
Either way, do your due diligence and use all of your resources to understand the franchise and to determine which is the best fit for you.