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.
The Mauryan art is believed to be inspired from Achaemenid or Persian influence. We can find a lot of similarities in terms of form and style in the inscriptions of Ashoka and the Persian king Darius.
EXAMIANS