I don't know if this should been the AA or DL forum, but since my basis for this post is to contrast a few key value differentiators between the two, and because I've been a veteran US turned AA LT Gold flyer, I figured it should go here. And, frankly, I had no idea that perks between programs could have some of the large differences so maybe there are others in a similar situation who may or may not want to test the waters elsewhere this early in the year. I found UA to be a lot more on par with AA, with DL giving some notable perks for even the lowest tier level (Silver)

My travel, like many here, is mostly weekly to the same place. For this year, 90% of my travel will be between PHL and a mid-continent city with weekly 3-4 night stays. In the 2nd half of last year, I stuck to AA for most of the trips. Some were nonstop, many connected in ORD or CLT due to timing. So to give me options for the new year, I opted for a DL status match which for an AA Gold was 8 segments/6250 MQM + $750 spend.

Starting in 2018 with equal status on AA (Gold) and DL (Silver), I decided to start with DL. My math showed me that my spend and segments would get me pretty far along within a few months. But what I noticed immediately about having Silver status on Delta was:

1.) Exit rows are available upon booking. They aren't blocked like AA MCE until T-24 hours to departure. So, 95% of the time I've been able to snag a good exit row
2.) DL Comfort+ seating is fairly expansive and after a few trips, I was getting the upgrades to C+ and even F at times on some off peak mid week trips.
3.) Simplified boarding. Travelers needing assistance, followed by Diamond/Premium cabin, Sky and a few coach zones. The 9 boarding zones on AA has become maddening and a free for all at the gate. Who can keep track of that!?
4.) DL Onboard GoGo viewing options of movies/TV are pretty decent. The free imessaging/whatsapp/email option is also a nice perk (for anyone). I know AA GoGo only charges 2.95, but it's still a minor differentiator
5.) DL miles don't expire. While I do try to use or generate some activity in AA to keep them from expiring, it's nice to know I don't have to sweat that small detail with my DL balance.
6.) Redeemable award miles at DL's lowest level(Silver) are given at 7x dollar amount vs. AA's 5x. That leads to redeemable miles to use sooner.
7.) People complain about not getting soft landings when the clock strikes February 1, but DL has rollover elite miles (MQM). So if I get to 70K MQMs by end of year, I'll have already earned 2nd tier 50K (Gold) in the new year with 20K MQM's credited towards the following year's accrual. That's effectively a soft landing.
8.) Even with <40 minute scheduled connections, the flights have so far had a very good on time rate with minimal delays.
9.) No 500 mile e-certs required for upgrades! That's a small consolation, but notable.

I'm already passing the Silver threshold and should pass Gold by April. So far so good!