My assumption was that you wouldn't have beach chairs, coolers, towels and all the crap most of us tote to the Cape. So the Seacrest would work well. I've enjoyed staying in Brewster and Dennis (bay side), which is very quaint, but still close to activities, and has some nice beaches (if shallow).
I also find the stretch of the Cape on the arm to be pretty boring. The dunes are beautiful, and P-Town is a fun day trip, but the traffic up there is bad because there is one road in or out. The water is frigid. I like making a day trip to that part of the Cape, but not staying there.
It should be obvious that we all have different priorities and approaches when we go.