I've never liked El Fenix so I cringe a little at the comparison. (But I grew in SAT.)
When Sammy's opened in 1991, Uptown was a ghetto. There was NOTHING down there. It basically sprung up around them, which is kind of wild. I moved to Dallas in '98 and started going there with my roommate. Met the owner's son (now my extremely close friend) through my ex-wife, who went to HPHS with him.
At one time, Sammy's was pretty good comparatively speaking before craft BBQ took off. It was better than Sonny Bryan's or Dickey's -- back when Dickey's was the OG location and maybe a dozen or so other places around town. And there wasn't much else. My buddy opened a second Sammy's in Preston Center that I helped him run for 18 months between newspaper and insurance careers. Like I said, my affinity for the Prichard family probably skews my feelings but that is about the nicest Highland Park family you will ever run across. The downtown Sammy's will always have a place in my heart as long as my buddy owns it.
Is the brisket world class? No. But it's not bad. And he's not charging $35-$40 per pound. And I stand by the sides -- baked potato casserole was practically invented there. The okra is legit as is the potato salad (if you like mayo potato salad -- I like to just a little bbq sauce to punch it up), onion rings are made from scratch (and to order) and Apple Pie is fanfuckingtastic. You can also eat lunch in there for less than $25, which has gotten impossible to do at many BBQ places in this state.
EDIT: /csb time. My buddy's parents used to be in the movie business. They used to do the low-budget type movies but they were ultimately put out of business by VHS. His grandfather (I think) produced Attack of the Killer Tomatoes or some shit like that. They used to own the Highland Park Theater. They went belly-up on that but his dad was a great backyard BBQ guy and his buddies said they'd stake him to open a place they could all hang out at. That's how Sammy's came about.