I think it depends on what of campaign you want to run.
Rise of the Runelords is fairly traditional D&D type fair.
Shattered Star is Pathifinder’s version of a megadungeon in some respects.
Second Darkness has a ton of great ideas in it, but is a hot mess on execution. If you’re doing a total re-write though it might be worth thinking about.
Wrath of the Righteous is awesome but very specific. You want to kill demons here’s your chance. It fits together plot wise very well though all the way from book 1 to Book 6. Many APs have an issued where the BBEG doesn’t get introduced until late in the game.
Curse of the Ceimson Throne is very, very good despite the side trip to Scarwall. But it has issues with the opening. The player motivation piece is tied to an NPC who likely doesn’t survive book 1.
Iron Gods you’re familiar with. Structurally that campaign works well and has some great set pieces. It’s vers peanuts butter in my chocolate though. Your players have to lean into the tech stuff to really get the most out of it.
Reign of Winter has an issued where where you almost feel bad for the supposed BBEG and your players are essentially ensorcelled to work for someone who they are going to want to kill. But the actual adventures work and book 5 is a gem.
Mummy’s Mask is very pulpy, very D&D meets The Mummy (1999). It’s a good time and book 2 is great.
I really like the opening idea of the first two books of Legacy of Fire. Djinn aren’t often the focus of a campaign so there’s some unique monsters you get to play with you don’t use. A trip to the City of Brass is on the cards in that series.
If I were going to pick one to convert to 5e my first choice would be Rise of the Runelords. It best fits the assumptions of basic D&D tropes wise. If I were going to pick the one I’d really want to do it would be Wrath of the Righteous. That campaign is oozing with flavor but it’s demons all the time.
If I were picking something I was rewriting from scratch I’d honestly look at Shackled City. It’s got some default assumptions to deal with, like it was written for 6 players, and it’s a slog, but the core premise is engaging enough and if you can sell the idea of Cauldron as home and get them invested in it, the setting will sing.
Curse of the Crimson Throne is the same. Get them invested in the city and the whole thing becomes extraordinary. Curse also doesn’t have the hide the bed guy until late in the campaign problem. She’s front and center from book 1 on. There’s also some support material revolving around the spirit possessing her that would allow you to make some real neat additions to the campaign and expand it to level 20.
