I believe simple is always better. I would go for the first design. Another simple design is to have your water split and half go to the right side which houses your protein skimmer and heater and such and then you can direct less flow to your refugium with the center being your return. An advantage to this is you can keep the nessary height of water in your proten skimmer section and have your refugium section filled almost to the top.
Check this out to see what i am talkinga bout