So first with the commercial lever...
I used what I have around the last week, which is more developed coffees like Caffe Lusso GMC, LionShare, Duomo from Black Oak. Dragonfly Lean Hammer, and Some Dapper Lion Espresso I had in the deep freezer. All easy to extract coffees with the exception of Lean Hammer being a bit lighter roasted.
Comparisons are not scientific in any way. Both machines require a different grind. Of course, the Leva requires almost a full hour to come up to temp. The DE, about 5, and the portafilter is definitely ready to go by the second shot. The Leva certainly wins in looks and silence, but that's not really what I'm comparing. The time factor will always go in the DE's favor. One morning, without any prompting, my girlfriend went ahead and made her own cappuccino instead of waiting for me to wake up. She worked her way thru the menu intuitively, since I hadn't really gone over it with her in detail. I was rather impressed by that.
Both using the Classic Lever profile and tweaking any of the general flow/pressure profiles to suit, work fine. The results in the cup were very much the same, maybe a bit more crema with the Leva. The Leva leaves a bone dry easy to knock out puck, the DE is soupy and messy. The Leva is also less prone to spatter.
I think when it comes to the lighter roasts, the DE will show more of it's advantages. Because my Leva is a dipper, the pre-infusion pressure is tied to the boiler temp. I can't get a low, slow pre-infusion that I'd use with a light roasted coffee, paired with a higher boiler temp for an extraction that isn't sour. But with the DE, since they're separate functions, I can achieve both.
I have little doubt that the Speedster and the DE with line up similarly. There's not a lot of tweaking available on the Speedster other than controlling line pressure pre-infusion time, it just looks pretty and delivers amazing shots. I'll focus the lighter roasts on those machines.