Viharas were for the purpose of living, Chaityas were assemblies for the purpose of discussions. Further, Chaityas were with Stupas, Viharas did not have stupas.
Towards the end of the reign of Rajadhiraja Chola, he sacked the Western Chalukyan capital Kalyanapuram and assumed the title Kalyanapuramgonda Chola and performed a Virabhisheka under the name Vijaya Rajendra Cholan.