Hey, trust me, Cowboy came in swinging first, but you're both irrational as hell. "X char can [insert move here] 99% of Y char [insert move here]" is almost always a dumb talking point. We're not robots, we're human beings and if you have a good tool, it becomes a factor not a guarantee in a match. Sinestro having a good d2 is a solid point that is almost balanced out by saying Batman's jump is quick, he has aerial mobility options and and has the advantage of being hard to anti air as a cross up attack due to the speed and hitbox of the move. Yet both of you use that as "Sinestro can't anti air Batman" and "Batman can't jump on Sinestro". It's silly.
Your assumptions are probably closer to the truth, but I'm just not a fan of most of the talking points, they sound far too concrete. From my neutral point of view, the biggest point Batman has is that he can punish B12, which is clearly a problem but also takes a certain tool that Batman must activate first. At the same time, Sinestro can convert many hits into a very disadvantageous position for Batman, and Batman can do very little to stop Sinestro offense up close without using a bat. You both have silly oki, so that's a wash. Really, it seems like if Batman has a trait out he gains quite a few options, but if he doesn't or Sinestro has his own trait out, things can get hairy quickly and neither can really afford a hit. Sounds like a wash to me because there are a few variables that can constantly swing back and forth over the course of the match.
This sounds different to me then, say, the Aquaman match for both, because they have nothing to threaten Trident Rush with and their formerly deadly oki game doesn't work out quite as well due to his trait. There are very little situations that don't come up daisies for Aquaman, which is a problem that both characters face and why it's commonly cited as a difficult match up. Clearly, they lack for options there from the character select screen, but it doesn't seem to be the case here. There's a lot of interesting factors/situations will take place over the course of the match and seems to be mostly dictated by a player's ability to make the most of one or two opportunities. Neither of you seem to be able to coast on one thing, which probably means its closer to a stalemate.