Content by Kai'lore, Spooky, o-DarkJester-o, Orange-Bell, T0nkaTruckDriver, Written by T0nkaTruckDriver, Edited by T0nkaTruckDriver
There are several emerging trends in the Mech Tau community. While all generally lumped under the title "Mech Tau", these variations offer subtly different play styles that each appeal to different people and offer different advantages and disadvantages.
Purist
Characterized by its lack of Kroot and absolutely no static elements. This list offers the most mobility and some interesting tactical possibilities. The lack of Kroot and reliance on Firewarrior Squads means you'll have lots of skimmer chassis on the table resulting in heavy dilution of your opponent's anti-vehicular firepower. This idea can be tailored a number of ways, but the emphasis on extreeme mobility means a loss of firepower that is often difficult to overcome. As a result of this, many Tau Commanders who play this style of army rely heavily on the Fish of Fury tactic.
Balanced
The Mech Tau army as it's described in Codex: Mech Tau. Kroot give us cheap and durable (when infiltrated into 4+ cover) scoring units. While somewhat reducing the mobility of the army as a whole, the Kroot special rules and assault ability add a huge new dimension to the tactical possibilities of the army. The inclusion of Kroot also has an interesting dynamic on the rest of your forces. By providing a minimal 'firebase' of sorts, the Kroot take some of the focus off the Firewarrior squads, reducing the expectations placed on them. In this army, Firewarrior Squads often fill a 'clean-up' role, whereas Firewarriors in an army without Kroot often find themselves leading the charge. On a table with minimal area terrain, the Kroot will often be less useful since they rely heavily on that 4+ cover save for their durability.
In Your Face
Characterized by Crisis Suits loaded out with powerful short ranged weaponry (often Helios) and lots of Kroot, this army likes dukin' it out up close and personal. With this many Kroot on the table, assaulting is a viable option against wounded or isolated squads and can even be attempted with the S5 Battlesuits. Firewarrior Squads start the game with their afterburners on high, looking to get up and unload with as many pulse shots as possible in support of other assets.
Hybrid
This army seeks to use the 'best of both worlds,' combining the mobility of a Mech list with the raw efficiency of a few static elements. Furthermore, by entrenching those static elements in a nice bunker or ruins, you can make them a durable focal point for your opponant to fixate on. A Monat Broadside and a medium sized squad of Firewarriors can often seem like much more of a threat than their 150 points represent, especially when the other 9/10 of your army moves 12" per turn and can't be caught. This often results in your opponent charging your small static element (often with much more than 150 pts worth of troops) while you decide whether to shoot him up on his way across the board, or leave his squad to finish off your troops putting them out of position and unable to contribute to the remainder of the battle.
A variation on this strategy uses a Monat Broadside as the only static element. Placed in 4+ cover and surrounded by much larger and more imposing threats, he's durable enough and 'harmless' enough to often be ignored for the first turn or two... which is usually just long enough for you to eliminate the Las Cannons which are the only real threat to him. A smart opponent will realize that his Las Cannons have 4-7 other much more pressing targets in the early game and that the Broadside is only 75 points, has a 2+ save, 2 wounds and a 4+ cover save... which when shot by a BS4 Las Cannon only has a 28% chance of dying. And if he does decide to shoot at you, take comfort in the fact that every Las Cannon that goes his way is a Las Cannon that's not shooting at your tanks. This play style is often affectionately referred to as "IC BIN MT!" or, I Can't Believe It's Not Mech Tau!