What is better for seb derm lotrimin (clotrimazole) or lotrimin (clotrimazole) ultra?

Either. Either one can be used. Both of them are different low percent anti-fungals that are over the counter. However, depending on where the seborrheic dermatitis is located, different formulations might be more effective. For example, in the scalp, over the counter ketoconazole or prescription strength works well even combined with a topical corticosteroid.