In synastry if you have a conjunction that crosses the signs how would it be different from one in the same ..?

Technically, the progressed sign carries on some characteristics of the one beforehand, especially in the early degrees, which is what gave rise to the idea of 'cuspage'. Depending on the aspects in this particular case, if the conjunction is still within a three degree orb, the energies should still be almost as strong as a conjunction in the same sign. The main difference would lie in the attitudes and certain likes of both people but in regards to the two of you (or the two you were speaking of) together, this particular aspect is still a very nice aspect to have for anyone :)