Looks like it's kind of late for a reply but lacking any other response, I will throw out some thoughts from my view. I should say upfront that I've not used the Cerge's style so can only look at it and add some theory. I used the Grigg's style as he drew it up and have been very satisfied so never changed when I added more tanks and reactors. When I find something that works really well I resist the urge to "improve" it. I find that is a way to totally mess up the design.
For judging the two, I go back to what I want and that gets down to cost, how well does it work and what potential downsides can I see. Then I like to have options if I want to use the design for other size tanks or situations.
Cost-- I'm a DIY guy and always have PVC and glue handy. That makes a Grigg's a natural for me but if I started from scratch, I can buy 18" of pipe, fittings and glue for about the same as a house filter costs. I don't bother with the purple primer when using new pipe and fittings that are not oxidized or dirty.
How does it work-- Both seem to satisfy most users.
Potential downsides-- Both seem to have a few users who have trouble. One big concern is the way they can both cut flow going through the filter. The Grigg's can be made better on this by NOT using any 90 degree bends in the waterflow. A large sweeping curve in the tubing and going straight into the reactor seems to be solution for this as well as using large enough fittings to avoid cutting flow. Not sure how this works out with the Cerge's style as the water has to flow in and then up and out. I do use a 90 at the bottom so that it can set on the floor and avoid strapping it to the stand. I do like to adjust the pipe size and length to fit what I feel is better for different size tanks. Eighteen inches of 1 1/2" PVC works well for 125 gallon but I use smaller for 55. I just want it plenty large but not use a crazy amount of space.