I think you've hit the nail on the head: it's not a question of whether a heavier pack is better, but instead a question of whether the pack's suspension is suitable to your load. (Generally, the more weight you carry, the sturdier your suspension - particularly the hipbelt - needs to be.)

In the end, it's a question you can only answer by taking all the gear you carry on a typical (for you) trip, including food and water, down to the outfitter's. Load up the various packs you're interested in, and carry them around the store for a bit. (Try to choose a slow day at the store, so you aren't spreading out gear and interfering with their other customers.) If you don't have a nearby store, order the packs you're interested in from an online retailer, do the load tests, and send back the ones you don't want. (You shouldn't take them on a hike if you intend to send them back.)

I believe you should get the lightest pack that works with your load. For example, if the Blaze works, the Aether will work, too - but you'd want the Blaze. (I haven't seen a Blaze; I did take one trip with an Escape AC 60, but the suspension was about an inch short, and the top of the molded frame sheet kept digging into my shoulders. Other than that, it was a great pack.)

I've gotten my weekend weight down to just under 18 pounds, and find that an Osprey Talon 44 carries it nicely - but I've also got a Kestrel 48 for those trips where I want or need to carry a bit more. The main differences between the two are the number of features (outside pockets, mostly) and the stiffness of the hipbelt. The Talon hipbelt is very thin - comfortable for those 18 pound weekends, but it begins to double over at about 25; the Kestrel's hipbelt is stiffer (but still pretty light); I've loaded it with 30 with no noticeable effect.

Also, your build will affect how the pack carries. I'm older, and losing a bit of strength in my shoulders; if you're young and beefy, you may find that the pack that gives me problems at a specific weight will be a really comfortable carry for you. Again, the only wya to know is to go to the store.