Can you really even compare those two packs? The Amp is 2600 ci, made of heavy ripstop and dyneema, and weighs 10.6 oz. Its built to be lightweight and pretty durable.
The Revelation is 2000 ci, made of .9 oz Spinntex, and weighs in at a whopping 3.3 oz. Its built to be the lightest weight possible.
If you have a sub-5 lbs baseweight then I would say go for the Revelation.
If your baseweight is much more than that, or you don't exactly baby your gear, the Amp is probably a better choice. I don't know about the bear canister compatibility of either one though.
ULA Amp vs MLD Zip, or MLD Revelation vs GG Whisper may be a better comparison.