Different dialects of Irish have different ways of forming the verb. In Munster Irish, historically at least, synthetic forms (= person and verb in one form) - e.g. Táim, Táir, Táimid, Táid - were more common, while analytic forms (= person and verb given separately) - e.g. Tá mé, Tá tú, Tá muid, Tá siad - were more common in Ulster Irish.
Incidentally, 'muid' is also a bit more Northern; in the Southern dialects, 'sinn' - as in 'Sinn Féin' - was more commonly used.