Any lens that will fit on the XTi will also fit on the T5i. The Canon lens will work.
As for the Quantaray lens... that "probably" will work but I have to provide a word of caution...
All EOS camera bodies use electronics to communicate with the lens. Canon does not publish the specs that the camera body uses to communicate with the lens. That means 3rd party manufacturers have to "reverse engineer" the communication to build compatible lenses. Sigma and Tamron are probably the two biggest makers of 3rd party lenses and have perhaps the most success with making compatible lenses (nothing is more compatible than buying the Canon brand lens). But even Sigma and Tamron occasionally have compatibility issues.
They test these lenses with whatever crop of camera bodies is "current" at the time that the lens was designed. But sometimes many years later those same lenses that would work with an old body will not work with a new body because the body is using some aspect of the interface that the lens does not understand.
In some cases, you can contact the manufacturer of the 3rd party lens and send it back to them to be "re-chipped" or have it's firmware updated to current standards. But not all 3rd party lens makers and not all 3rd party lenses can be re-chipped or have their firmware updated.
So... "probably" it will be fine and you'll have no issues... but that's not a guarantee. IF you do have an issue, contact Quantaray and ask them if they can update the lens.
Tim Campbell
5D III, 5D IV, 60Da
