I came from Envoy and sat reserve for 90% of the time there. I've sat reseve 90% of my 6 years here. Reserve at American is definitely better.

-last day of reserve, LC is auto released at 10 am and SC is released after 6 hours of on call (if not used by that time)
-if you land on your 2nd to last day of reserve where debrief ends after 2200, and nothing is on your schedule at that time, then you are on LC your last day. It's nearly impossible to use you then.
-Once you are assigned a reserve trip, 99% of the time, the trip ends when it was scheduled and they don't add onto you. At Envoy before the newer contract, they'd send you out for a turn and keep adding on for 4 days. The 1 add on limit at Envoy was a game changer for me.
-The union has some good software to alert you of any open trips for today or tomorrow. I can live with less stress as I don't have to constantly check open time.
-The new contract puts us first on the upgrade list for first class. As a reserve, I fly broken trips a lot so there is more deadheading. I'd say I get first class 75% of the time.
-You can arrange your monthly schedule to 3 day blocks, which prevents you from doing any 4 day trips.

This new reserve system definitely favors the senior. When you are first starting out, you will be working a lot but your limit is 85 hours for the month. Once you reach 79.45 for the month, you are done (there is a caveat for the last day of the month). As a senior NB FO, I typically fly between 4-8 days a month, with many of those as 1 leg days.

Let me know if you have other questions.