HOBs are easier in terms of sliding out a cartridge, swoosh it in a bucket to clean it, slip it back in - you can't beat that for easy. BUT, the last time I needed to clean out the box of my Emperor 400 I was sloshing water all over the place trying to lift that thing off the back, high enough for the intake to clear, and carrying it to the sink. Luckily you don't have to do that too terribly often.
Fishyrican, you are right that these discussions can turn into a battle!
jevousdeteste (I'll try not to take your handle personally...
) I think the bottom line is that you might need just a bit more power on that tank, and you can go either way you want in terms of a larger HOB