Hi Tamás, I own a Portaspresso, in fact three of them, and a Bacchi, and an Otto for completeness.
The real difference is the portaspresso can use any source of hot water, Zip boil on my ship, or my Jetboil while camping, while the Bacchi requires not only a heat source, but a carefully adjusted heat source at that, as too hot will mean the brew water is too cold when the safety in the pressure chamber starts to "whistle", while too slow means it is too hot.
Te Bacchi makes good espresso, but best left to home use where you know the equipment, while the Portaspresso will work with any boiling water.
How the "Denver" affect influences the Portaspresso, I don't know.
Hope this helps