"Just out of curiosity -- what is lame about it at DC? DO other parks do something differently or is there more time?"
Just my humble opinion of course:
Discovery Cove is an absolutely beautiful park and a wonderful day. Let me say too that everyone in my group thought the dolphin experience was fantastic and one of the best experiences of their lives except for me and my husband. The dolphin swim is very short and very staged. // You really (and that's probably good for the dolphins) don't have a whole lot of alone time with just the dolphin -- the trainer is always right there telling you where to place your hand and what to do. And the distance you are pulled is quite short. // We're been to places with just you and the dolphin. You jump into the ocean in a 20 feet deep large coastal pen and no one else is in the water and the time with the dolphin is considerably longer and your swim is three times as long (mom and pop Key West place -- probably not even open any more. DH and I didn't meet till I was 22, but both of us did family trips to this place when we were kids and even have old home movies. Really cool stuff here.). We've been to places where you get to go underwater with the dolphin too on your swim, and it's not just a short surface pull (Vallarta Adventures Puerto Vallarta, Mexico -- It's called their extreme dolphin swim). Maybe we're jaded, but the Discovery Cove experience after those felt more like a photo shoot.
Most experiences we've seen are fairly similar to Discovery Cove (surface pulls -- typical experience in the Caribbean) but these tend to be not as supervised and a little longer. The two in the paragraph above were our favorites and the most different from Discovery Cove. DH and I too are a bit in the been there, done that, bought the T-shirt camp and usually these days skip these kinds of things ourselves, but pay for DS to do it if he'd like to go if we are somewhere where the opportunity arises.
My best guess not knowing the details of the local option for OP is that that one will probably be very similar to Discovery Cove, but have more dolphin time and a longer swim, but that due to the beautiful setting, Discovery Cove would be a more satisfying day overall. And if you have never done a dolphin swim elsewhere the dolphin swim part at Discovery Cove will be quite satisfying and feel pretty amazing too based on the reaction of other people young and old who were in our swim group.
SeaWorld from what I can see appears to take the best care of their dolphins and provide the most enrichment activities for them of any of the places we've been (the best of the best). They also have trainers around more than any other place making sure dolphins are handled properly and not stressed out by guests. The downside for the guest who has been elsewhere is an experience that feels a bit staged.