I see Rabbut is still peddling misinformation. All filter manufactures with the execption of Hagen aim for real world (pipes media) water turn over of 1 to 1.5 of the rated tank.
for example his favorite Tetra 1200 turns over 600 l/h rated for 500 l tank.
eheim 2217 turns over 735l/h for a 600 l tank. (both with pipes and media).
Your link, Bastables, made for very interesting reading
The EX 1200 is rated at 1200lph with media, no hoses.
The 2217 classic is rated at 1000lph with media, no hoses.
The classic has more torque, so with reasonable hose length of 4ft the inlet and outlet, they'd probibly push about the same
The Tetratec EX1200 holds 12l of media, taken from the website, the 2217 9l from Eheims website. The Tetratec has a wider surface area, so theoretically is more efficient, as contact time with the media in the tetratec is increased. The Clasics need their media layering, as I belive they ship without baskets? They aren't realy comparable in that respect, but I can see that mebe media choice is a little more limited in the clasics, as there is nothing to stop finer media mixing up with other medias in the classics, but the pro models come with media baskets. I suppose it depends on what you want from your filter, and the media you intend to use
In my application, the EX1200 is a better choice, as there is more media flexability and wider surface area, making for less cleaning. What the EX1200 lacks in torque, it gains in media volume and surface area, so they should both do a good job on resonable sized tanks. I aim for 3+ times an hour turn over through my filters, so 300l would be the biggest tank I'd put either on. As you know, I've had issues with Eheim before, so my choice of the EX1200 is more down to my faith in that brand. Both companies do good stuff, but the Tetratecs haven't yet been proven. Though Eheim are proven, they let me down when I needed them, hence why they aren't my preference
All the best
Rabbut