Keeping it in the footer elements will keep the emphasis of the powered by statement prominent. Since the top of the page will consist of the product (logo) branding you can avoid another logo for powered by in the same estate.
The conventional habit of people while going through any product page (any webpage for that matter) is top to bottom, and it is highly likely that the user may be drawn to the details of the relevant products while skimming through the page. Hence keeping "powered by" at the trailing end of the page will bring the user's focus back to the company providing the products, which makes it intuitive.
By trailing end I mean bottom right corner of the page which the user is most likely to give a final glimpse after reaching the bottom of the page.
However if you have constant margins/"empty space" on the left/right/both sides throughout the web page you can also dock it to the bottom left/right corner of the screen. For the simple reason, if the user chooses not the go to past half of the page the powered by logo may go unnoticed. So for a docked logo, irrespective of the number of products the user views he/she will always see who is it powered by.