There is, prescriptively, one minor difference to their pronunciation: the accusative singulars written with ـًا are pronounced -ā in pausal form, but with taa marbuta, the pausal form for the accusative indefinite is the same as the genitive and nominative indefinites (i.e. the case ending is null). So whilst the pausal form of مكتبا is maktabā, the pausal form of مكتبةً is maktabah (not *maktabatā). In my experience, though, whilst many native speakers would be quick to insist that the rules of pausa are always applied, in reality this is not necessarily the case. In particular, alif tanween is often pronounced -an even at the end of a sentence.
[flag]en[/flag] native| [flag]cy[/flag] mwy na chdi | [flag]fr[/flag] plus d'un petit peu| [flag]ar[/flag] ليتي استطعت
ég sef á sófanum!