AN 6.43 and KN Thag 15.2: unintentional oral transmission error.

 The verse sections of these two suttas should be exactly the same:

* AN 6.43: https://lucid24.org/an/an06/an06-v01/index.html#s43

*  KN Thag 15.2 

They almost are identical except for a handful of very minor discrepancies, perhaps a result of reciting, mishearing, and remembering a homonym.

But here is one error I found, that I think is noteworthy, and we can deduce which one is correct.

AN 6.43 has austerity and celibacy

Nāgaṃ vo kittayissāmi,	I will enthusiastically praise the ‘giant’ [, a perfected Arahant, by comparing him with a ‘giant’ royal elephant].
na hi āguṃ karoti so;	for he does nothing monstrous.
Soraccaṃ avihiṃsā ca,	Gentleness and harmlessness
pādā nāgassa te duve.	are two feet of the giant.
Tapo ca brahmacariyaṃ,	Austerity and celibacy
caraṇā nāgassa tyāpare;	are his two other feet.
Saddhā-hattho mahā-nāgo,	Earned-trust [in the Buddha] is the great giant’s trunk,
Upekkhā-seta-dantavā.	and equanimous-observation his white tusks.
Sati gīvā siro paññā,	remembrance [of Dharma] is his neck, his head is discernment—
vīmaṃsā dhammacintanā;	discrimination and thinking about Dharma.
Dhamma-kucchi-sam-ātapo,	the Dhamma sits in the digestive heat of his belly [, nourishment ready to be absorbed],
viveko tassa vāladhi.	and his tail is judicious-seclusion.

Thag 15.2 has sati and sampajāno instead

Nāgaṃ vo kittayissāmi,	I will enthusiastically praise the ‘giant’ [, a perfected Arahant, by comparing him with a ‘giant’ royal elephant].
na hi āguṃ karoti so;	for he does nothing monstrous.
Soraccaṃ avihiṃsā ca,	Gentleness and harmlessness
pādā nāgassa te duve.	are two feet of the giant.
Sati ca sampajaññañca,	remembrance [of Dharma] and lucid-discerning
caraṇā nāgassa tepare;	are his two other feet.
Saddhā-hattho mahā-nāgo,	Earned-trust [in the Buddha] is the great giant’s trunk,
Upekkhā-seta-dantavā.	and equanimous-observation his white tusks.
Sati gīvā siro paññā,	remembrance [of Dharma] is his neck, his head is discernment—
vīmaṃsā dhammacintanā;	discrimination and thinking about Dharma.
Dhammakucchisamāvāso,	the Dhamma sits in the digestive heat of his belly [, nourishment ready to be absorbed],
viveko tassa vāladhi.	and his tail is judicious-seclusion.

Thag 15.2 is probably wrong because sati and sampajāno is redundant

Sati here is both one of the feet, and the neck, with the head being pañña discernment. 

1) There's no good reason to use 'sati' twice in the simile, and AN 6.43 only has it once.

2) neck being attached and so closely related to the head makes more sense, than sati being one of the feet. Just as the frequently occurring phrase in all the suttas, sati + sampajāno (a conjugated t form of pañña indriya) has those two awkakening factors joined like siamese twins.

Conclusion

This sutta is a good case study of the kinds of minor errors that can keep into the oral tradition style of learning and retaining teachings.