Generally you only use about 5 Quanta Towers in a typical speedbow since you only need a certain amount of quanta, and the SNova's can usually provide enough to play every card in your deck, because you choose effective for low cost cards like the ones I put in. However, with Serendipity, this changes a ton, since you're getting a massive card increase, and a fair amount will be high cost cards. You don't want to not be able to play a randomed dragon for example just because you decided to skimp out on a few QT's.
Also one third of these use Entropy, which places a certain need for a continued Entropy growth. Plus, rolling up Dis Shield works a lot better when you have more towers to try to sustain that shield for the couple turns needed. I put in the Improved Mutation after a little bit once I started realizing every mutation effect I got would almost inevitably be hyper-effective, and that I had no 'Entropy creature' to use.