Bumping the discharge hose/pipe size up 1" above the pump discharge outlet is a good idea. If this will be out in the weather for the season (or more)...the corrugated pipe would last longer compared to the run-of-the-mill lay flat hose (think sun/UV damage). I would definitely use the lay flat hose IF this is a system that will get stored away regularly AND the hose is running down hill. Sometimes these lay flat hoses can get to rippling which causes it to pinch, especially if running up hill or over uneven ground.