Originally Posted by sealife
Classic does not have baskets so im guessing it's harder to clean and maintain.
But there's a big price difference between them.
That is pretty much the biggest difference. The classics are hand-packed so they are a huge pita to clean. That being said, they are a 30 year old design, rock solid and inexpensive.
The Pro 3's are a modern design, expensive but pretty much a dream to work with. The modular intake and flowbar sets are nice and flexible. Also, the dark gray is usually easier for me to hide than the one piece green sets that come with the classics.
All of the Eheim's are pretty solid from a build perspective.