Is there a practical difference between these theoretical derivations? – Imagine that ten men cohabited anally with a betrothed girl who is a virgin. According to the first way of learning, she is still a virgin after each act, since only the husband makes her a non-virgin with annal cohabitation, Therefore each man is to be punished by stoning, specified for violating a betrothed virgin. According to the second approach though, she is a non-virgin after the first act, and the next nine men are subject to a lighter punishment of strangulation.
Exactly what stage of cohabitation achieves kiddushin? Normally, for matters of infidelity and prohibited relations, the first stage of relations, member touching (discussed in another place) is considered the act. However, for kiddushin it is different. Since the man's intent is for complete penetration, he achieves kiddushin only when this is done. Practical difference? – Can he inherit his wife, or can he bury her if he is a Kohen.
Since there are two stages in a marriage, betrothal (dedication) and chuppah (bringing the bride into the husband's domain), a question may be asked: if one does betrothal through cohabitation, does it also effect the second stage of marriage – that is, is the second cohabitation or a chuppah still needed? After multiple arguments back and forth, it is concluded that cohabitation only accomplished betrothal, but a chuppah is still required.
Art: Wedding at the Photographer's by Pascal Adolphe Jean Dagnan-Bouveret