Pros of Lower Boards (drop or drop-through)
What is the advantage of a board with a lower center of gravity?
JW Boards with a lower ride height make life easier for beginners, cruisers, freeriders, or anyone who prefers a more stable, driftier setup. Decks are either lowered by a drop going down, changing your foot placement and weight distribution,
or your trucks being mounted through the board (drop through).
If you're really looking to be closest to the ground, the double drop mounting style combines a dropped platform and drop-through to get you as low as possible
Pros of Drop Decks
Anything with a lower standing platform from the Funbox LTD, the DB Paradigm, Omen Barbarian or Blackdog Jelly are all drop decks that feel great for different people or for different styles of riding. Essentially, the drop in the deck distributes your weight over the trucks more evenly resulting in slightly less response in the trucks but an overall lower center of gravity. When having a drop deck you are forced to compromise the foot standing platform for a longer wheelbase, since you aren't able to stand directly on top of the trucks, the standing platform is confined in between the trucks at all times which allows for a more stable ride. When it comes to sliding things get a bit easier, having a much lower center of gravity you have a much lower coefficient of traction. This may be a little hard to understand at first but when you think about what happens when you slide it begins to make a bit more sense. When you slide you are pushing your board sideways when it doesn't want to/isn't intended to. So when you slide, your board automatically wants to tip downwards against the hill. If you have a tall board it will tip much more than a lower board, this is why when you have a topmount it is much easier to highside and your wheels overall feel much more grippy. Having a drop-deck eliminates the amount of overall tip resulting in a much easier kickout and hookup of a slide. Also having the board closer to the pavement is nice for pushing and commuting because you don't have to step as far down to push making for a much more comfortable cruising/commuting deck.
Cons of Drop Decks
Obviously some people have their preference of drop decks vs. topmounts and there are a few reasons why some people would choose a top mount over a drop deck. Yes, having a lower standing platform allows for much more stability and ease of slide, however those aren't preferred for certain disciplines. If you are into downhill, taking sharp lines and having as much grip as possible at all times, a drop deck would not be the best for that type of riding. If you go into a corner at a high speed with a drop deck, you will not wobble off your board, but you will not necessarily be able to take the best line possible. When you kick out your slide you will slide much more than you would like to and you won't be able to turn your board as sharply as you would like. Having a longer wheelbase and more dispersed weight over the trucks will not allow you to turn as sharply as you would with a topmount.
Pros of Drop Through Decks
Drop through decks are mainly used for cruiser style setups, simply because most of the benefits cater towards that type of riding. Since drop through boards aren't as structurally strong, and typically flexier than a topmount or drop deck style deck, taking them up to higher speeds isn't as preferred. Since drop through decks get you very low, they serve a similar purpose as drop decks in the sense that they are much easier to push with in comparison to a topmount. Usually drop through decks are a little flexier than most, like the Loaded Dervish and the DB Coreflex, which are both awesome decks for low speed cruising, carving, and dancing. Stiffer downhill style drop through deck like the Landyachtz 9 to 5 or the Blackdog Belial serve a similar purpose to stiffer drop decks. They are very easy to slide considering that the center of gravity is much lower as well as it makes them much more stable.
Cons of Drop through Decks
Like stated above, drop through decks are not the strongest because all of your weight is distributed mainly on the 8 bolts holding the trucks to the board. This is why most drop through decks are flexy and suited more towards carving and cruising. This doesn't mean they are bad boards, they just cater to a different discipline of longboarding. Beyond the structural integrity, drop through boards are very drifty. For freeride, it makes initiating slides and sitting over them easier, but if you need any grip for corners or any other technical maneuvering, drop throughs are a losing idea. Therefore, downhilling with a drop deck will not be a good idea if you have any technical riding in mind. Along with the driftiness, the amount of truck response from drop through is the least out of all mounting styles. Because you are mounting the trucks physically through the board, you are getting nowhere near as much leverage due to the natural height and your foot's increased distance from the trucks. So, if you need any technical performance, such as taking corners or maintaining grip, maybe stay away from a drop through deck!