Not much to tell beyond what WP has already said. Mounted in front of a LF driver, the tweeter can only be aligned at the XO point if electronic delay is used, while it can be physically done with the HF driver behind the LF's if properly designed. If the LF diaphragm acts as a horn extension, then its angle(s) and diameter determines its BW gain/polar response, so bigger is better. The abrupt/flexible change at the horn's metal mouth to LF diaphragm transition causes reflections back to the HF horn's throat, modulating its output somewhat, as does the LF's excursion, so won't be nearly as 'clean' as a well designed/built separate horn.

Bottom line, where space is a problem and/or the listening position is relatively close, the coax is a better choice IMO than a separate two way of comparable XO point/slope, but as the distance increases and/or the XO gets down around where our hearing acuity starts to roll off pretty good (~1 kHz), then an aligned two way separates makes more sense to me.

GM