In the way of a totally personal opinion, canister filters seem to do a significantly better job of removing solid waste and chemicals from aquarium water than HOB filters. This is probably due to the fact that canister filters can hold a much larger amount of mechanical and chemical filter media than the 'cartridges' the HOB filters use. On the other hand, canister filters cannot 'compete' on an equal basis with bio-wheel biofiltration technology, if for no other reason than the fact that the bio-wheel of an HOB filter has access to an unlimited supply of atmospheric O2. This isn't to say that filling a canister filter tray with bio-noodles or bio-rings can't result in adequate biofiltration though.
IMHO the real question boils down to the types and amounts of 'waste' that you anticipate will be generated. If you plan on 'overstocking' your tank, or planting your tank, then a canister filter is going to do a better job keeping the water free of solid and chemical wastes. On the other hand, if your tank is to be lightly stocked and not planted, then a canister filter is probably 'overkill'.
There is also a 'best of both worlds' option that you might consider. Perhaps install one of your Penguin 150 HOB filters on your new 30 gal tank and leave one Penguin 150 on your 29 gal tank primarily for biofiltration, and also install a small canister filter on each tank as well to take care of the solid and chemical waste ! In the past I have run a Penguin 330 in conjunction with a Rena XP2 on a 55 gallon tank, with very good results. A Penguin 150 in conjunction with a Rena XP1 or Fluval 104 or Cascade 700 or any other small canister filter should do a magnificent job on a 30 gallon tank. Of all of the small canister filters, the Fluval 104's flow rating is probably the best match for a 30 gal tank size, as all of the others may have to be 'throttled back' to avoid turning a 30 gal tank into a maelstrom !
If you're partial to Marineland products (i.e. Penguin filters) you might also want to take a look at a HOT Magnum -
http://www.bigalsonline.com/catalog/product.xml?product_id=22139;category_id=1721;pcid1=2885;pcid2= , which essentially performs all of the functions of an external canister filter but makes for a simpler installation on smaller tanks, and is also notably less expensive than the smallest external canister filters. Running a HOT Magnum in conjunction with a Penguin 150 on each of your tanks would be a 'near perfect' match capacity wise.
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