Comparison Between Sword Lann and Spear Lann

Introduction
Please note that the comparison assumes max level Lann played by an experienced player. A low level Lann with mostly untrained skills played by a new player will have different results. However, that is just the learning/training period that the new player can easily experience on their own and also grow out of it quickly. They can also peruse leveling guides for Lann for that learning/growing period.

Survivability
Swords:
 * Using Nimble Dash, Sword Lann can have a longer uninterrupted period invulnerability
 * Using Thousand Needles normal stab, it is easy to chain up long series of Slip Dash with minimal delays.
 * This is limited by stamina.
 * Most Sword attacks cannot be canceled by Slip Dash, so mindful foresight is important for a Sword Lann.

Spears:
 * Spear Dash has small but unavoidable delay between each dodge. Some multi-hit attacks cannot be fully nullified by Spear Dash's invulnerability frame and player must physically dodge out of the attack's reach.
 * Fury Infusion (rank 9) means limitless stamina, hence limitless dashes.
 * Spear Dash can cancel Moon Splitter and Grand Hurricane at any time, which is very useful to correct mistakes or react to unforeseen events (ex: another player turned the boss quickly).

Damage Output
Swords:
 * Heavily reliant on Gliding Fury and empowered Lightning Fury for maximum dps, which in turn pressures Sword Lanns to keep up with bosses' critical resistance.
 * When Risky Wind is optimally utilized with sufficient player skill and attack speed, Sword Lann will actually achieve higher dps against a boss that fights back than a punching bag boss (like Kraken head).

Spears:
 * Moon Splitter spam is the easiest way to achieve high tier DPS against a punching bag (like Kraken head), but maintaining dps against bosses that fight back is a complex problem for Spear Lanns. The faster, more aggressive the boss is, the exponentially more difficult it is for the spear Lann to maintain high dps.  However, this can be overcome with sheer player skill (expert knowledge with good timing and wise choices/adaptations in different attack combos).
 * Belclaire's Blood Pact buff is a very significant element in Spear Lann DPS. While it is a free dps boost against docile/slow bosses, it is a very high-risk-high-reward buff when fighting aggressive bosses that only becomes practical after mastering the boss.
 * Unlike Risky Wind where purposefully timing a dodge into a hit is required to maximize damage, the difficulty of maximizing Spears damage an be sidestepped by consumable and gear. Buying and spamming Merc Recovery Potion or pumping Lann's Defense to mitigate damage.  Then use Slashing High to prevent knockdown.  At that point, most bosses become punching bags.

Range and Fighting Style
Swords:
 * With the exception of Fanning Slash, most of Sword Lann's attacks have short range, but Lann moves forward a lot to increase to practical reach of the attacks. (Ex. Pummel Storm has very small hitbox, but Lann moves forward a bit so the actual reach goes further than the starting position)
 * The primary play style of Sword Lann is to get crit and use Gliding Fury, Lightning Fury as much as possible. Since Slip Dash is so powerful and Risky Wind highly rewards its usage, the most powerful way to play Sword Lann is to stay next to the boss (almost) all the time.  A master Sword Lann will weave in the optimal attack patterns while nullifying all of the boss' attacks (which feeds back into doing more damage due to Risky Wind).  A good Sword Lann is always aware of his position and uses the movement portions of his attacks to help with his positioning.
 * Stamina is a bigger factor for Sword Lanns since Fury Infusion is not available. Sword Lann needs make up for this by being mindful of his stamina bar and availability of Slashing High.

Spears:
 * Spear Lann's attacks come in much greater variety and they each have very specific uses. Some of attacks by itself can be used almost as a standalone play style. Though one thing that all Spear Lann play style have in common is to properly manage the buffs.  (Fury Infusion, Blood Pact Blood Pact, Slashing High, etc.)
 * Spamming Moon Splitter is the way to go for bosses that rarely attack the Lann for whatever reason. Throw in a few Gliding Fury when the boss is chasing another player or Spear Dash a few times is all a Spear Lann needs to do in these scenarios.
 * Spamming Grand Hurricane while moving tactically to exploit a boss' slow AI, slow turn speed, or weak attack range/speed is often enough to kill a boss on its own.
 * When fighting very mobile, very aggressive bosses, with extremely wide attack reach (ex: Keaghan), the Spear Lann must utilize everything in his arsenal to perform well. In these situations, the Spear Lann must properly choose which attacks they will, as well as when, where, and how they will use it.  A Spear Lann in this case must be played with even greater diversity and resourcefulness than the Sword Lann to perform well.

Hit Drag
For both weapons, Gliding Fury and Lightning Fury are not affected by Hit Drag.

Swords:
 * Double Crescent, Rising Crescent, and Blade Tornado have very noticeable Hit Drag. So the best multi-hit attacks to proc crit are also the slowest when Hit Drag is applied.  Fanning Slash and Gust Sting (when stationary, not sprint smash) also have Hit Drag.

Spears:
 * Belclaire, Silent Hawk, and Moon Splitter all have very noticeable Hit Drag.
 * Grand Hurricane does NOT have Hit Drag even though it looks like it would.

Gear & Stats
Swords:
 * Sword Lanns are reliant on reaching Crit Cap to maximize the chance to proc Gliding Fury and Lightning Fury. Sword Lanns need be extra mindful in picking weapons based on its base crit, and enchanting for +Crit.  On related note, Willpower is also useful to raise crtis, but only noticeable in high amount, so all sources should be utilized to raise it, including Gear, Leveling, Will Mastery, and Titles that give +Will.
 * Twin Swords tend to have higher balance and lower crit, attack than Twin Spears.
 * Due to the lack of Fury Infusion, it is more important to Sword Lann to increase max stamina and stamina regen.

Spears:
 * Spear Lanns value all the main stats normally, and because of Fury Infusion and Blood Pact buffs, it is easier for Spear Lanns to have sufficiently high stats to be viable in a fight.
 * Twin Spears tend to have higher crit, attack, but lower balance.

So... Which Should I Pick?
Weapon choice is a stylistic decision and ultimately, most Lanns have a favorite but will play both. So picking a weapon is mostly a challenge only to new player who is starting out. For that case, this is the best way to go:

1) Go with Twin Spears (when it becomes available), but only rank up Fury Infusion to max. Learn the other skills but only buy the cheap ranks (ex: 30AP for Rank E) or as pre-requisite to buy other skills.  This allows you do kill things fast and move through the level fast while saving your AP until you have more experience with the game to decide which weapon.

2) When you start dying, try switching to Twin Swords. This is when the boss is tough enough (to your natural skill level) that the survivability trade off and learning curve actually become noticeable for you.  Take some time to try out and compare the two styles.  Learn the different tricks and cancels as described in their respective skill pages on the wiki.  Decide which you want to main and spend the AP you saved up accordingly.  If you still can't decide, prioritize putting AP into shared skills like Smash Mastery, Critical Hit, and Gliding Fury.  It is perfectly viable to master both styles simultaneously, you will just need to budget your AP, and grind more for weapons (a non-issue if you have friends/guildies to whom a few mil for lvl 60, 70 weapons is spare change).