I haven't been to SCI, but I was talking to my outfitter in his booth at DSC in 2020 and asked him about the other shows. He said that DSC was where he does most of his business as it attracts more Texas hunters than SCI.
I'll add another vote for DSC. I've been to both DSC and SCI and both are overwhelming if it's your first convention.
SCI definitely costs more as it's only open to members, not the general public. As a military man, I particularly appreciate that DSC offers free admission to military and LE.
Added bonus if you attend DSC, you can come to the AH.com dinner party. Hopefully it'll happen in 2022... @PHOENIX PHIL hint hint...
If you decide on Dallas it can be a bit overwhelming so do little strategizing. You can get a list of exhibitors in advance and also a floor layout with booth numbers. Take the time before going on the floor to write down who you want to see and what to accomplish. Keep notes. Like a kid in a candy store the show can be fun but overwhelming. Do a little planning. Oh, and wear a pair of comfortable walking shoes