Both are sick boards, the monarch was my favorite board ive ever ridden...until i hopped on the conspiracy. within one boat set and a few laps around the cable, the conspiracy was my new favorite. the conspiracy has a faster glide speed and a little faster edge hold than the monarch, and is just a hair grippier than the (finless) monarch to give great edge hold for air tricks. the conspiracy also has several extra durable features about it to make it last a really long time. it has a fiberglass rope infused with resin running along the edges to make a totally solid, seamless edge. theres nothing to split open. it can even be hit with a hammer on the edge without breaking. also the fins are made of ABS plastic, a dense material that can be slid down to little nubs and not have the foam from the core show through. these are really tough, i slid my conspiracy for 2 weeks at OWC and Ski Rixen this winter and other than some tiny surface scratches and swirl marks on the bottom, it looks like new.
the monarch has a double lap construction meaning the top layer wraps around the edge to the bottom and the bottom layer wraps around to the top. this make it more resistant to impacts and delaminations than a normal construction. I dont think it has the abs fins, but no doubt its a great board, it was very good to me!
Bottom line, both are great boards, but the conspiracy will hold up longer on rails due to the reinforced construction.