The internal structure of the fixed port design allows for a very direct gas flow through the first stage, providing optimal performance. The fixed port design is also typically the most compact as well as being lower cost when compared to a similar swivel turret design. The most common objection to the swivel design is that it adds O-rings and moving parts to a more complex gas path, theoretically being less reliable and of lower performance.
Regardless of port design performance, streamlined hose routing is a significant concern for experienced divers, where careful hose routing can make a noticeable reduction of drag. The absolute cleanest hose routing for some regulator package configurations is only available using the swivel turret design while for other configurations an equally clean or cleaner routing might be available using a fixed port design; especially in doubles, sidemount and stage technical configurations.
However, in our experience with quality regulators these theoretical concerns about reliability and performance are irrelevant. All the regulators offered by Dive Gear Express are high performance products with proven reliability, and the reality is that both these designs will more than meet your expectations. The choice is largely a matter of personal preference.