The main difference between the Denali and the Denali Evos is that the Denalis stay the same width for the entire length of the snowshoe, while the Evos are tapered in the back to decrease the likelihood of stepping on one shoe with the other. Because of this difference in width, the tails for the Denalis will not fit the Denali Evos, so make sure you are purchasing the appropriate tail for the appropriate model.
Both models come in a regular version (
Denali and
Denali Evo) without the heel bar, as well as an ascent version (
Denali Ascent and
Denali Evo Ascent) with the heel bar. The coloring seems pretty variable- black, red, gray, or blue options are available although not all stores carry each color, and not all colors are available with each model.
They are indeed one size fits all, with the intention being that you can use the tails (sold separately) to increase the surface area as conditions and body weight require. The size of the tailess snowshoe is in about the low to mid-size range of snowshoes. The Denali and Denali Ascents have 4 and 8 inch tails available, while the Denali Evo and Denali Evo Ascents have 6 inch tails available.
I've had a pair of Denali Evo Ascents for several years now, and I've really liked them. The binding straps are starting to break, but they are easily replaced. There is definitely a trade off with the binding straps being somewhat flimsy, but it is very easy to put the snowshoe on and take it off without getting your hands/fingers cold. The snowshoes grip incredibly well, and the ascent bar makes a huge difference on uphill climbs. There is definitely no reason not to pay the extra money for the ascent version of either model of snowshoe, as it is well worth the money.
They definitely are not for everyone though- it's a mountaineering snowshoe, and while they perform well in rugged icy terrain, the limited size decreases their effectiveness in flat deep snow. If you're planning on doing a lot of winter mountain climbing, I'd say go for them. If you're just looking for a pair of snowshoes for flat lowland hikes, I'd say go with a more traditional type of snowshoe.
As for ultimately deciding which shoe to go with, I'd say that if you are small or average build, go with the denali evo ascents and the tails. In the high peaks, I've found myself hardly ever needing the tails for my evo ascents in the winter (5'11" 175 lbs). If you're of a larger build that needs the extra surface area, it'd probably be better (and more comfortable for you in the long run) to go with the denali ascents instead.
I personally have no experience with the Lightnings, but I've heard lots of good things about them- especially that they are lightweight. They look like they wouldn't be as durable as the Denali's, however, and I'd rather carry a little more weight of my feet if it means my snowshoe will last longer. But I have absolutely no personal experience with the lightnings to back that opinion up.