Well, they don’t know what’s their origin, they don’t know what their ancestors did. The older one gives a brief picture while the newer one is a more floral one. Poor guys…Can’t do much. Or is it multiple attempts to create a history for them, knowing that they are just petty rulers who were suddenly propelled to power? Rajendra Chola uses the title Varman, the main Pallava title – is it legitimacy or is it that they are actually Pallavas? By linking to Ikshvakus, are they saying their Tamil legacy is not sufficient to legitimize them? Or, are they directly stating they are not Tamils and even if they are, they are too ashamed to be declared so in public?

Valenjeri Plates OF Parantaka Chola(~920 AD) (http://tamilartsacademy.com/articles/article28.xml)

Let this dynasty of Cholendras which planted its lotus feet on the crowns of all the kings, which proclaimed by their swords, the expansion of the foreheads of sovereigns of the entire universe encompassing the seven seas, protect all the world.
From the tender lotus, issuing from the naval of Murari, emanated Brahma. Though he was humiliated in a moment by the light that surpassed the soft braided hair, Marichi was born of him.
Kasyapa was born of Marichi and from him came Surya (avicharya marga) who adorns the entire world with his pure associates.
After many rulers having enjoyed the world attained godhead,was born in that famous family, the great Lord Usinara by name.
The king, the ornament of the family, who gave away immediately his own flesh when approached by Lord Agni in the guise of a vulture, and relieved the dove from torture and suffering, was born as Sibi.
In that family took place the birth of Karikala Cholendra whose orders made the slopes of Himalayas, the abode of Kubera (the Lord of riches); following whose orders the water-course of the river Kaveri, was controlled by the embankments on either side and whose orders made the city of Kanchi full of palacas reaching the clouds.
A spider made a very small, thin and beautiful prapa (protection) for Siva by a web of threads, issuing from its mouth. When Lord Hara was pleased at that, it was born as Kochengannan in that royal family.
Orriyura known for his marvellous valour was born. His son was a veritable fire to the forest of enemy kings.
Aditya equal in splendour to Kubera, was born of him. He shone as a moon to the lotus like faces of enemy queens.

Tiruvalangadu Copper Plates of Rajendra Chola(~1020 AD)

(V. 4.) The eye of the three worlds was the Sun from whom sprang the sprouts of all (families of) kings. From him (i.e., the Sun) was born by concentration (manana), Manu, the first of kings whose name became (thus) conformable to (its) meaning.
(V. 5.) Great Ikshvaku was born (as) his son ; of him, in great battles the enemies of gods (i.e., the danavas) were greatly afraid. The three worlds, though completely immersed I the ocean of his spotless fame, (still) enjoyed extreme delight.

(V. 28.) (People) say that Dushyanta was an ornament of the race of this (king). His son was Daushyanti (i.e., born of Dushyanta) Bharata. To him was born a son named Chola after whom the Solar race on this earth became illustrious.
(V. 29.) Him (i.e., the king Chola), learned men described as the generous lord of gods (i.e., Indra) who incarnated on earth (on seeing that) the glory of his own (i.e., Amaravati) was humbled by the varied and lustrous riches of the Chola country.
(V. 30.) Cholavarman’s son was Rajakesarivarman (‘the lion among kings’) who split asunder with (his) nails (viz., crooked knives) the elephants (viz., crooked knives) the elephants (viz., his enemies) and (was) the cage (wherein resided the goddess) of prosperity.
(V. 31.) Rajakesarin’s son was king Parakesarin by whose fire-like anger the enemies’ forces were consumed.
(V. 32.) Thenceforward these two names indicative of (their) suzerainty were alternately borne by the Chola (kings) in the order of their coronation.
(V. 33.) Parakesarin’s son was king Chitraratha ; his son (was) Chitrasva ; to him (was born) king Chitradhanvan.
(V. 35.) Having come to know that king Bhagiratha engrossed in penance brought down (from heaven) the river of gods (i.e., Ganga) (to earth), this king (also) desirous to fame brought her (i.e., Ganga) to his dominions under the name Kaverakanyaka (i.e., Kaveri).
(V. 36.) In that family was (born) Suraguru who was the hereditary abode of the maiden, the Lakshmi of victory. This king having conquered by his glory the god of Death in his own territory acquired the name Mrityujit.
(V. 37.) In his race was born king Chitrartha called Vyaghraketu from his banner-cloth bearing (the figure of) a tiger, who was a store of great heroism and who wore as an ornament on his head the flowers of the dhataki (Grislea Tomentosa).
(V. 38.) The Treta-age having come to a close, a son of this king known as Narendrapati became the ruler. The diadems of (subordinate) kings dropped down their gems ; (because their) fastenings had become loosened by the constant rolling at his footstool.
(V. 39.) From him was produced the head-jewel of the powerful Solar race, (king) Vasu, who was the cause of the destruction of the demons (and) who (known) by the significant surname of Uparichara moved in any direction he liked in a celestial car which was presented (to him) by the lord of gods (i.e.,Indra).
(V. 40.) At the end of the Dvapara (-age) was born in the family of this head-jewel of kings a conqueror of all hostile kings named Visvajit.
(V. 41.) In his race was born Perunatkilli who was the receptacle of all sciences, the abode of (the goddess of) Prosperity, who was worshipped by the diadems of all the rulers of the earth which were set with rows of precious gems.
(V. 42.) In this (king’s) family was born he, the leader of all the lords of the earth, the foremost of the great on account of his virtues, the king who renovated (the town of) Kanchi with gold, who had established his glorious fame by constructing embankments of the Kaveri (river) and whom (people) called Kalikala because (he) was (the god of) death to the elephants (kari) (of his enemies) as also to the Kali (-age).
(V. 43.) In the family of that (king) of extensive glory was born the emperor Kochchengannan who bore on his arm the earth (extending) as far as the Lokaloka mountain, whose tremulous eyes were as blue as the petal of the blue lily (and) the bondage of (whose) spider-body and cut off by (his) devotion of Sambhu (i.e., Siva) the conqueror of (the demon) Tripura.
(V. 44.) In the illustrious family of that (king) was born Vijayalaya of praiseworthy prowess, whose footstool was battered by the diadems in the rush for precedence (ahamahamika) of kings desirous of prostrating.
(V. 47.) (After him), (his) son king Adityavarman, the asylum of the wise, a Dhishana (Brihaspati) (in learning), energetic, always bent upon removing evil and adhering (himself) to the path of the righteous, protected the earth.