I think the following sums up many of the key points:
Ryan Parkinson's answer: Better for what? For the South Koreans and the terrain they operate in and the physical restraints of their military and government? Good enough to be exceptionally superior to the point of ridiculousness to anything their North Korean cousins are able to field? Requires ...
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To this I would also add:
- In the case of Poland the M1A2 SEP V3 is already on order thus there is a benefit on focusing on single type
- The M1A2 benefits from a much larger allied and industrial base - 7 other operators including the USA (incl Europe based forces) and likely to grow soon as more Eastern European countries are seeking Abrams vs just one in the form of Sth Korea for the K2
- Further to the above, the large size/multiple operators offers greater investment potential moving forward
Finally I would add (and this is just a personal opinion, though one based upon experience) that the level of after market support seemingly provided by the Sth Koreans on other systems (both airborne and ground) leaves a lot to be desired.
Few corrections to the Quora post you've linked :
No, the Korean sabot rounds are not slower than 2-generations older M829A2. Only the 105mm K1/1E1/1E2 series of tanks operates rounds slower than 1,600 m/s muzzle velocity. In fact, both the older K276 and the newer K279 are faster than 1700 m/s
Also he talks about tungsten and DU rounds and their characteristics which are basically true, but he didn't consider that Korean APFSDS rounds are able to self-sharpen, ie doesn't mushroom when penetrating unlike conventional tungsten rounds; one of the biggest strength of DU rounds compared to tungsten. The actually advantage M289A3 and A4 has against K279 are superior L/D and weight, which also means more energy, but not because of muzzle velocity. As a side note, Koreans have pursued faster muzzle velocity in the past through technologies like ETCG but have soon followed suit of the Germans and went with SCDB instead. Not to forget are other technologies like composite DS.
Lastly, he mentions range but doesn't mention M1's horrible fuel economy, which I definitely would if you want to compare the two.
About your own points, I should inform you that with programs like Wilk, Poland is searching for partners to develop and produce, either a variant tailored to Polish requirements of and existing tank or their own model. What is known to me is that Poland is currently favoring cooperation with the Koreans in that regard since they are the most eager to get their product sold. From what is recently known after the visit of Polish MoND, they've also inquired the possibilities of joint development program of a wheeled ACV after being showcased and offered of K808, mentioning they are more interested in their own product rather than importing already existing ones. Of course, who knows how these deals will eventually turn out, but at least that is the current situation. Possibly, Poland licenses M1A2 instead.
Moreover, since what is actually being offered to Poland is K2PL, a vastly different variant of the tank to ROKA K2, those key differences mentioned in the Quora post are quite irrelevant in the first place. Sales of the ROKA specification base K2 has only been discussed as a contingency plan for if US disapproves sales of M1A2. We all know how that went.
Last but not least, I'm not sure where you are getting all those information regarding Korean defence product since the only major defence contract to Australia was and is the Huntsman, which isn't even delivered yet. One that I could think of is the RN Tide-class, which has seen delays, but talking about ground systems, all or most of the K9 operator seems to be happy, some even ordering additional units. Obviously I'm happy to be corrected if you have actual sources.