Reviewing this as someone who has extensively played the Japanese heavy line since their release in 2015, and 3 marked every single Japanese heavy tank.

Review is based on patch 1.17.1.

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Pros:
- The 3rd highest HP pool in tier (2050)
- Thick frontal armor thats very resilient against same-tier standard ammo and lower tiers
- 10 degrees of gun depression
- Both guns have the highest alpha damage of all tier 9 heavies
- 14 cm has huge alpha damage (600) and decent penetration
- 15.2 cm derp has ludicrous alpha (680) and devasting HESH shells with 900 alpha


Cons:
- Largest tier 9, very easy to hit
- Very slow with painfully low specific power
- While the HP pool is good, it's relatively low all things considered - its only 50-100 higher than most tier 9 heavies. Its not like the Type 5 that gets 30-40% more HP than a lot of tier 10 heavies
- The armor can be wonky in many ways - it has weak hull cheeks, the front itself can be penetrated with standard ammo with good RNG, the turret armor is quite poor, and its very weak against premium ammo and TDs
- Both guns have poor accuracy, gun handling and DPM
- 14 cm has rather mediocre premium ammo and suffers from very high penetration drop off over long distance
- 15.2 cm lacks conventional high-pen premium ammo and has very bad accuracy, making it incredibly ineffective against certain tanks, the HESH shells are also super expensive. It also has limited gun depression over the front (6.5 degrees)
- Gigantic ammo rack that is quite literally bigger than some tanks. It will be broken very frequently, especially with weak hullcheeks. In addition, the Type 4 also has frontal transmission, making it possible to damage the engine through lower glacis plate
- Pretty painful stock grind


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Equipment: Gun Rammer, and then 2 of following: Improved Hardening, Turbocharger, and Vertical Stabilizer. I'd personally run Rammer / Turbo / Vstab for most maps, and then Hardening / Rammer / Vstab for small maps. You can drop Vstab for both Turbo and Hardening, but unlike the Type 5, the gun handling isn't that good, so the loss of Vstabs can be painful.

If you use the derp gun, then a more dedicated gun handling-based loadout, like Gun Rammer / Improved Aiming / Vertical Stabilizer is also an option.

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The review itself:

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When the player gets past the mindbogglingly awful O-Ho and reaches the Type 4 Heavy, they're immediately greeted with good and bad news. The good news is that the Type 4 is a significant upgrade over the O-Ho. The bad news are that the Type 4 is STILL possibly the worst tier 9 heavy in the game. Sure, it's better than the O-Ho, the Japanese heavy line really fell into the pit at higher tiers. The Type 4 is an extremely flawed vehicle, and has a very low winrate and popularity for a reason.

The Type 4 is very much like the Type 5. Its huge, slow, unwieldy, with very wonky armor. That being said, while it plays very similarly, there are some significant differences. Generally speaking, the Type 4 has better firepower than the Type 5, but worse survivability and mobility. The armor is wonkier as its slightly easier to pen with standard ammo, has hullcheek weakspots that can be penned even by tier 8s when exposed, and premium ammo ruins the Type 4's day even easier than the Type 5's. Its also slower, with much worse specific power and reverse speed. On the other hand, the Type 4 gets better guns. Sure, the 14 cm doesn't handle nearly as well, but 600 alpha is suddenly much scarier at tier 9, the DPM is overall better tier-for-tier (though it still sucks), and 290 mm premium penetration is at least somewhat okay at tier 9. And the 15.2 cm, being nearly the same gun a tier below, is actually semi-usable, though it's still a meme pick.

The Type 4 has the same goal as its brother - get as close as possible while losing as little HP as possible, and try to deal heavy blows with its massive 600 alpha. Its not as easy, as the Type 4 has much lower HP pool, but the Type 4 is arguably even more powerful than the Type 5 in its ideal situation, due to ludicrous alpha damage on both guns. You overmatch weak roof armors. You expose your front and peek corners instead of sidescraping. Its especially important with the Type 4 - the weak hullcheeks mean that you want to avoid sidescraping altogether. Actually playing the Type 4 is pretty simple - its planning things ahead and positioning thats tricky.

One thing that does set the Type 4 apart from the Type 5 is that the 15.2 cm derp gun is actually...usable. Sort of. Its still incredibly flawed, but unlike the Type 5, the Type 4 actually has by far the best alpha damage in its tier. Remember how I said the 600 is massive? Yeah, 680 completely eclipses EVERYTHING else at tier 9. Even the 50TP, which is the alpha damage king of all tier 9 heavies if the Type 4 is left out, still heavily gets outtraded by 680 alpha. Just like with all the derps on the Japanese heavy line, you absolutely need Intuition skill to make the gun work. The penetration with both shells is also much easier to work with at tier 9. 252 mm AP is actually okay instead of pretty bad, and the Type 4 can also find more opportunities to pen its HESH shells at tier 9, and the 900 alpha hurts a lot more here. That being said, the derp gun is really flawed. Its bit like the derp on the O-Ni - you're picking it to gamble. In bad matchups, the derp gun is worthless. In good matchups, it kicks ass. However, the reward is there. The derp is so bad on the Type 5 simply because the reward isn't good enough - it's almost the same gun as this but at tier 10. The derp gun is also uber expensive to run - another thing to keep in mind. I'd say the derp is a more fun gun to use than the 14 cm, but again, it's a pure meme pick and very, very unreliable. It's objectively a terrible choice, but it's just "usable" enough where you can call it a "bad meme", instead of being just "bad" like it is on the Type 5. The 14 cm is a much more competitive gun. It's honestly a pretty decent gun, and still hits stupidly hard, so the Type 4 is still pretty unique with it.

Lastly, there's two small things to keep in mind. Type 4 has two loaders instead of two radiomen, which can be frustrating, as the previous tanks had two radiomen. Secondly, because of the Type 4's hull layout, you can "in theory" reverse sidescrape. The Type 4 is too clunky for that 99% of the time and people can just shoot premium ammo at your turret anyway, but it can be a funny gimmick in a tricky situation.

Like rest of the higher tier Japanese heavies, the Type 4 Heavy sucks. It sucks really hard. Calling it the worst tier 9 heavy is not a hot take by any means. However, the Type 4 is maaaaybe the best out of tier 8-10 Japanese heavies. I feel like it's not THAT far off from being worth two stars instead of one. Unlike the O-Ho and Type 5, it has a pretty decent gun that is also really unique due to its insane alpha damage. In addition, the derp gun is somewhat usable as a shitty, yet potentially hilarious meme. Also unlike the two, the Type 4 isn't strictly outclassed by another tier 9 heavy. There isn't a single other tier 9 heavy that can match Type 4's hilarious alpha damage. However, being unique doesn't change the fact that the Type 4 does indeed suck. Most players won't find the Type 4 fun to play at all, as goes with rest of the higher tier Japanese heavies. Like the O-Ho and Type 5, the Type 4 needs serious buffs to be viable again. Hopefully Wargaming will eventually do that, because these tanks are really unique and they could be so cool if they were balanced right.