I've used a handful of canisters including the Magnum HOT (220/250) and the Magnum 350...
I absolutely love them for "water polishing" using the micron cartridge. I always wrap the cartridge in either the blue sock used with Magnums or quilt batting. Anything to catch "the big stuff" which makes the cartridges last much longer...
I would not rely on a Magnum (either model) as my main source of filtration.
I'm a fan of the AC 110s... 2 on a 75 gal works excellent...