A few people have posted with problems on the Puck. A very few people have posted with problems on the EZ. I'm just going from memory, but my perception was that the Manufacturer of the EZ jumped all over it and made things right. And the other 98% of EZ owners seemed happy from day 1.
I sent an e-mail with questions to the EZ folks, and got same-day or next day replies. I did the same with the Puck, trying to verify if I could tweak timing myself, or if the "custom PC mapping" applied only to some other Diablo products, because the web site wasn't 100% clear. I don't believe I ever got a response from Diablo. Could be my fault - wrong address, or server problems at my end (wouldn't be the first time).
I like the description of the Puck, but I recommend you do your own test, contacting both companies. Also check around for best prices, sometimes you find a sale. There's even a few used EZ's around as some go to more aggressive fueling boxes - but for my money I'd just get a new one 'cause it's worth having exactly the right one for your truck and a two year warranty, plus a 60 day "money back" guarantee. All JMO, of course.