I bought an MLD bug bivy last year, intending to switch to it plus poncho on a long distance hike last year, but it took too long to arrive to use that way. I've since purchased an SMD Gatewood Cape, and bought SMD's (different type of) bug net tent to use with it.
When I originally picked the MLD unit initially (Serenity Shelter), it looked from the pictures to be a better design to me --- shaped more like a tent, and better shaped to fit under a tarp, which indeed that latter is true. But apart from how well it works with the Gatewood Cape, it turns out that I like the SMD unit better for a couple of other key reasons.
(1) Despite a picture on the MLD site of a guy (sort of) sitting up inside their net tent, I can't sit upright in mine. This makes for a much more constrained feeling, indeed more like a bug bivy than a small bug tent. I'm 5' 10" tall, and I do get more of my height in my torso than average, but still --- I'm not all *that* tall, and even pushing hard against the mesh I simply cannot sit fully upright. On their website they say that the front height is 38". When I sit up, the top of my head is at more like 39-1/2", and (despite what some of my friends say) my head doesn't narrow to a point like a triangle.
In the SMD tent, however, I can quite comfortably sit upright.
(2) I bought the MLD bug shelter for use with my Golite poncho tarp. In retrospect, I don't suggest this, as in anticipated wet (and especially wind-blown wet) weather a person wants to stake the foot end of the poncho tarp close to or just directly to the ground, which doesn't work well with a net tent whose rear height is 20". Of course the rear end of the net tent doesn't have to be fully extended, but then I think you end up with a sagging structure that might be a bit more of a PITA to work with (though I didn't do much testing of this). I think the MLD unit is fine for a short-torso person or a person that doesn't care if they can sit upright, and who uses a conventional (larger) tarp.
The SMD bug tent isn't designed to go under a standard tarp, but for a Gatewood Cape owner it's perfect. Okay, maybe I'd like it better if it had a slightly higher bathtub floor, and it could use one additional connection point (opposite the door) to the Gatewood Cape, so maybe not for me absolutely perfect, but I'm much happier with it than doing various half-situp exercises inside the MLD unit.
I passed my MLD net tent off to my (not as tall) daughter, hopefully it will work well for her.