Some of the Kitech/Zhengdefu 30cm kits are actually quite good (I've heard they're scaled-up copies Skywave 1/700 kits with a lower hull added), though the aircraft and 1/48 armour kits from the same manufacturer are uniformly awful! I have the Kitech Spruance-class DDG (around 1/550 scale) and it has a good level of detail for the scale, and fairly clean, flash-free mouldings. This is the only one I can speak for personally, but I'd imagine their other modern USN and Soviet/Russian ships are similar.
I'm not too familiar with the Academy kits, but I have seen a range of small Academy kits of WW2 battleships (Bismarck, King George V, Yamato etc.) which were about 30cm in size, they appeared to be fairly recent mouldings but were very basic + simplified in terms of detail.