This is like asking "I need to commute to work, what car should I drive?." There are many factors at play with creating and running a SaaS-based business, and

This is like asking "I need to commute to work, what car should I drive?." There are many factors at play with creating and running a SaaS-based business, and often technology plays a minor role. Even less important is how fast your chosen backend runs. By the time you run into a technical scaling problem where you are stuck with a less-than-optimal solution, you've already solved much, much harder problems like finding customers, scaling a team, raising money, etc. So decide how big your org will get, look at the skill sets of developers available in your local area, and partner with someone that has experience with both. Then let them make the decision on the tech and trust them. Then you can focus your energy and attention on what's really important for your new business.