Speed dueling means the games are over faster and, more importantly, each card has more of an individual impact. Deck building is nuanced because each one of your 20 cards has to really contribute.
If the deck size was 30-40, say, and there was more board space, everyone would run a bunch of the obvious tech cards - Autonomous Action Unit, Shard of Greed - and that would make each deck a bit samey.
Now that you have to trade between obviously great cards that don't directly contribute to winning and your core set of cards that win you the match, it's a nuanced game.
I've managed to pull every UR from the first box. Still need a few SRs then I can focus on the water mini-box for a bit.