No experience with either, but Penn Plax stuff in general is the most poorly made, most prone to failure equipment I've ever owned. In my opinion, it is best stayed away from...
I have both an Eheim 2213 and a ViaAqua 300. For the cost and features the Viaaqua is well ahead of the eheim classic range, yet much cheaper (and mine came with a free heater). The ViaAqua also comes with more tube accesories, more hose, swivel hose outlets, and a better media basket system than the Eheim classic range. As for the other brand you mentioned, I have not seen it yet.
The real test will be to see how many of these Penn Plax canisters are still in operation in ten, twenty or thirty years... as many Eheim Classics are. My experience with Penn Plax products is that two years would be amazing longevity, but maybe they've got their act together.
I have the Penn Plax Cascade 1000. When I was looking for a new cannister filter, I went willing to shell out the bucks for the Eheim. Cost has never been worth sacrificing quality for my fishies . Anyway, LFS owner that I know and trust recommended the Cascade over the Eheim models, actually, any cannister filter in the store. I saw that the store also was in the process of switching over from Fluvals to the Cascades for its own tanks. The owner told me that the Cascade incorporated some of the best features from the big names and was very well constructed. I, too, had my doubts since Penn Plax is probably best known as maker of plastic plants. So far, it's a great filter. Large capacity, nice amenities, easy as can be to prime, an easy clean, quiet. Though I can't speak for its longevity yet, I would highly recommend it nonetheless. The price is hard to beat, too .
In a marine set up, when you clean your filter do you can all part of it. I heard your not to clean the hard rocks at the bottom and how often should I clean it. Thanks for your help