One thing to take into account is cleaning the pipe work.
Every couple of years/months/weeks you may want to be able to completely take out the pipe work for a yearly/monthly/weekly thorough cleaning. Thus having some way of getting all the water out of the pipework and getting the pipe work apart easily will make this job a lot easier. Of course you could design it to be cleanable/brush'able in place.
I have seen many people assemble and glue pipe work in place, looks wonderful and is 100% leak proof, but once glued was impossible to remove from the tank for cleaning.