OP they are of different quality and design. The amount of machine work that goes into the sparrow is much more intensive than the Guardian. One is a monocore, the other is encased baffles. The sparrow is considered by many to be the best 22 can out, and the G22AL is more of a budget minded can. Both are great though. One is just a little nicer than the other. Both offer very easy to clean designs.
I have Guardians of all flavors in stock and more Sparrows about to be here. Spectres are in stock too.
I went with the AAC Element 2. I paid $360 plus taxes but got the $200 rebate. I don't have it so I can speak for the can itself. But I hear good things about it.
I have an aluminum guardian that I upgraded to the stainless Kestrel baffles (which all the stainless guardians have now BTW). It is larger than the sparrow which I actually like, it is not noticeably louder than the sparrow, and with the stainless steel fully encapsulated baffles disassembly and cleaning is a snap.
For ease of cleaning I would go with a stainless can, but beyond that pick the one that best fits your budget/needs. I'm happy with my Guardian and I would buy another one if I needed a second rimfire can.
I"m looking at 22 cans as well. I am pretty set on the sparrow but what advantage is there with the spectre? It would see 90% use on 22lr pistols/rifles (my guess would be pistols mostly, as bulk pack is subsonic thru 4" barrel from what I've been told). Mostly Ruger Mark II hosts. Occasionally 10/22 and 77/22 and maybe contender hosts. I have 22hornet and 218 bee that might be fun to thread but I can't see them being as much fun to shoot as they are not subsonic...
so am I on the right track to be looking at a sparrow? cost isn't a big deal, once you add in the wait time and tax, the price difference is moot to me.