I had a Penquin Bio-Wheel (think it was the 150 but not sure now). And I also have three Aquaclears (all are 70's). I would go with Aquaclear all the way. The bio-wheel would stop spinning often, even after just cleaning it & the parts around it. Very irritating. It made more waterfall noise than any of my AC's even though one doesn't fit properly on my 75 so sits really high above the water. I keep all my tanks water level really high though so keep the noise down.
AC's are easy to replace any part needed. Not sure about the Penquin since it quit working after 1 year of purchase. Much easier to customize the media in the AC. Didn't try with the Penquin since I was new to aquariums & didn't know about all that. From what I can remember about it, it didn't have a lot of room behind the filter cartridge. Can use much cheaper filter media material in the ACs. You can modify the Penquins cartridge to just add the blue bonded pad but it didn't work as good and just too much hassle.
I can remove the impeller from an AC without removing it from the tank, dumping water or taking the motor off. Just need to take the basket out, the impeller cover off & then grab the impeller. Being able to remove the motor is a plus also, not only for replacement if needed but for cleaning also.
AC's have a flow adjustment don't think the Penquin's do unless they've changed them.
My Penquin had a square intake tube making it harder to customize it, for example wanting to extend or use something like an ATI Pre-filter. Not sure if they're still made that way or not. Now realize it's a big negative for me.
The biggest negative I have about the AC .. it doesn't always start up when plugging it back in. It's not just me as I've seen it mentioned frequently on the web. It's more of a hassle when I'm home .. I just use a wooden stick & "help" the impeller start. But if I'm away when it happens, such as might happen with a temp power lose, it will probably ruin it. Of the 3 AC's I have, only have this problem with one.
I might be just a bit biased I guess since my AC's are all old and still work while my Penquin died so quickly. But the ACs are just so much more versatile.
