I wouldn't be surprised at all to see the Bengals get blown out, but I wouldn't be shocked if it went the other way either. Just two very inconsistent teams. I have no idea why exactly the Texans have been so miserable lately, but I've got a very good idea why the Bengals have: the offensive line.
Cincy's offense is all over the place, and that inconsistency starts with a wildly inconsistent o-line. What's frustrating is that it should be a strength for the Bengals and if you break it down individually then it looks pretty good. Andre Smith at RT has quietly developed into easily one of the best RT's in the league, Zeitler at RG in his rookie campaign has already developed into a guard well above league average. Whitworth has not had a great last couple years, presumably because he hates gingers, after being one of the top LTs in the league, but he hasn't fallen off that much; he's still pretty good. Boling at left guard is young and little raw with a lot of talent though and if easily passable. They've had a lot of turmoil at center this year after Cook went down in the preseason. They pulled him back off IR and he started a couple games, but it didn't go over spectacularly. Then there is the likely starter for the Texans game UDFA Robinson who has been just a flat out steal. He's very good, but he'll occasionally still make some rookie mistakes.
So center is a little dicey and that's the heart of the line, but overall the group has a decent amount of experience together especially when Cook is in at center - because while this is Boling's first season as a starter he saw a decent amount of work during his rookie campaign. So, I guess most of the stability issues do come down to an undrafted rookie center (and to a lesser extent someone on the left side fucking up occasionally) in what is individually an outstanding line. When the line is on though they are a fucking force in both the pass and run games. The Texans and Bengals both have huge strengths on the defensive front and both have had shaky o-line play as of late, so I think the play of the big guys on offense is ultimately what is going to decide this game.
I'm really fucking excited for the game though. 23 years without a win in the playoffs and never won a playoff game on the road, but after waiting 3 decades for back to back winning seasons the atmosphere is electric.
edit: I think the Bengals have a clear edge in special teams, so if it's a close game that's one more thing that could tip it over to a win.