Ent-schuldigung is rather for stages in theatre or for newsspeakers in broadcasting/tv. In common German language, you'll probably hear "En-tschuldigung" most often, or even "'Tschuldigung" because it's much easier to say. The more you reach a geographical region which neighbours a state with Slavic foreign language - where "tsch" is a quite common phoneme - the more often you'll here "En-tschuldigung". In a region which is more close to a language which doesn't have a common "tsch", you'll rather hear "Ent-schuldigung".

A proper separation "Ent-schuldigung" requires aspiration of the voiceless "t" (and perhaps a glottis afterwards, I'm not quite shure about that), whereas "En-tschuldigung" does not have separate aspiration of the "t".

Ent-schuldigung is rather for stages in theatre or for newsspeakers in broadcasting/tv. In common German language, you'll probably hear "En-tschuldigung" most often, or even "'Tschuldigung" because it's much easier to say. The more you reach a geographical region which neighbours a state with Slavic foreign language - where "tsch" is a quite common phoneme - the more often you'll hear "En-tschuldigung". In a region which is more close to a language which doesn't have a common "tsch", you'll rather hear "Ent-schuldigung". "Ent-schuldigung" was the normative choice made for formal Hochdeutsch. However here in Austria, we most often say "En-(t)schuldigung" or even "Tschuldigung".

The voiceless aspired "t" sounds very Northern German for our ears.

A proper separation "Ent-schuldigung" requires aspiration of the voiceless "t" (and perhaps a glottis afterwards, I'm not quite shure about that), whereas "En-tschuldigung" does not have separate aspiration of the "t".