This storm by-pass … more economical to fly around as opposed to getting over it? Or passenger comfort - or both? Just curious?
Comfort/safety.
This flight was conducted with a Bombardier CRJ-700. Maximum certified ceiling is 41,000 feet but if you’re fully loaded, you’d get there, but you’ll have to step climb (a lower altitude first to burn off some fuel and be at a lower weight) before you make it there. Even with the NextGen CF34-8C5b1 engines on the CRJ-700, it’s still not an immediate unless you’re already at a lower weight.
For this flight, given the short range, their cruising altitude is only FL260 (26,000 Feet), so you wouldn’t even be getting that high. With thunderstorms, tops can be up to FL600 (60,000 Feet) and the higher the tops, the more likely you want to avoid it. At FL260, they would probably be flying right through the middle of it all. Considering also the short distance of the flight, diverting around it will only add an additional 14 minutes to the flight time, not something to lose sleep over, especially when it can make for a more comfortable ride, not just for the passengers, but the flight deck crew as well because they don’t have to deal with a thunderstorm. With this routing change, it also allowed them to fly at a higher altitude, FL320 (32,000 Feet) and it might have also burned the same amount of fuel as if they went at FL260 direct.
There are many things to consider, very rarely is it one specific thing or another.
Hope this helps…
Can you guess which one of us is a CFI?
And this whole time I thought he was just good at pulling random stuff out of…uh, you know… and making it sound good…
Well…that too 
Tops in that area were reported to be around FL400 so there was no point in trying to go over them. And even if they could get on top the extra climb fuel burn vs. going around would be a wash. Added time would be pretty much a wash too as the slow speeds in a climb offset the added distance/time to go around.
Even going over the top in the clear can be bumpy as the air is displaced upward from the boiling TS underneath. Bottom line…besides the dangers…TS scare people/passengers. 
Going around reduces complaint letters that can get back to the Chief Pilot, who then calls in the Captain of the flight in question, and…
Looks like that link, or at least the image, is broken. Here’s a link to the flight
depends on what kind of plane you are flying. A fast jet can go around it easily (and with little penalty), but can also get above it. If you have a small plane, and can’t get above the tops (which as said earlier can get quite high), you are in for a ride.