I think PEX looks like hell when itís in stalled and then try looking at it after you do a recirculation system on a home run system. You end up with a bunch of Tís, a bunch of 90*ís, extra manifold (some of the time I end up with valves to control the flow on some of the runs), check valves on each home run return, and a pump 24/7 or a timer system.
With copper you just have to double back with a 1/2 off the main run and use a check valve. If itís 2 stories then you have a second 1/2 run and a second check valve. I insolate all of my hot and cold water lines when I run copper.
If you can show the math on how a home run PEX system is cheaper then copper on a recirculation system then I would love to see your math. Why not do the math on a single story 2.5 bath and kitchen. Open basement with the hot water heater on far side of the bathrooms.
I donít know about where your at but where Iím you canít get away with not using 90*ís. The inspectors will not pass a PEX install unless all of the runs are more or less in straight runs. PEX must be supported every 20 inches.