I have been experimenting with both as DIY projects lately. I was looking for anyone with long-term experience using either to share their knowledge with me (best design, flow rate or situations where one is superior to another).
I currently have a DIY under gravel Jet setup with my 35 Hex, 3" of red fluorite caped with 1 1/2 " of course sand powered by a 200GPH pond pump . My other is a 50 tall with DIY under gravel filter covered with 2" of standard aquarium gravel, powered by air stone.
I used to keep undergravel filters run with powerheads in all my tanks supplemented by cannister or hob. Dispite 50% plus weekly water changes with gravel vaccuming and a close eye on feeding habits my nitrates rose quickly. A fellow cichlid keeper convinced me to get rid of them and go sand. Tried this on my biggest tank and 2 months later I switched all my tanks over. Glad I did. Ditrius sits on top making it easy to vacuum and my nitrates stay half what they used to be between water changes.
Now the jet system seems like a different beast. Filtering water and then pushing it into the substrate to force debris out of the substrate makes a lot of sense. How are the 2 ways working for you. More details on both setups regarding stock, plants etc. Plus what the water changes are on both tanks and nitrate readings