public ad is better in hindi or eng???

Its completely depends on target group as you may also have to choose any other language if want do marketing exercise in any other region where respondents doesn't understand hindi and english, so first of all you have to check the main language of respondents and there literacy rate.

Depends on your target market to whom you want to communicate, if it is a regional market, regional belt, hindi would be preferable, otherwise in metro cities, english is what is recommended. Hope this resolves your query. Feel free to put up more queries. In case your query is resolved please clos