RE: Acid 74 vs Acid 73
I would say the from a shape point of view have vey little in common. On the other hand, the "performance concept" ie what the boards are built for and how they should work is almost the same.
One can say that the two boards arrive at similar type of performance from totally differnt directions. To be more specific, the PA73 is really based on the EVO 70 but "drawn out" in differnt ways. It still ends up feeling very "classic" in its behaviour, but there is a tad of "EVOness" still there wrt how it softens up chop. The PA74 is based on the PA80, but has softer rails and a slightly rounder outline. It has v bottom and a straighter rocker and a tail that both feels more solid under your foot but at the same time kind of loose. The PA74 has a straight line feel that is more "over the fin".
So again, there are lots of little differences betwen these two, but most of the time they kind of do the same thing but with different kind of feedback to the rider. That said, I personally think the PA74 is a much nicer board with a more "harmonic" feel and to me that little differnce is worth a lot. Wether you will feel the same and wether this is worth the extra money for you is very hard to say.