The problem with the old modules is, for the most part, they aren't particularly good. Kind of boring, in fact. Almost universally they're of the "move into a room, have an encounter, kill monster, search for treasure, rinse repeat." Occasional trap interspersed. Zzzz... and the story lines are pretty dull.
Which is precisely why I am adapting instead of converting - I can use the same synopsis, spice up or at the very least streamline the whole thing, and throw in as much DCC jazz as I can fit.
T1-4 is kind of interesting but some of the encounters were pretty stupid. It just all felt like a cobbled together mess, to me... this is probably because I was running it for 3.5.
It tends to feel a bit cobbled together and messy in AD&D too, and suffers greatly from what I call NRHM syndrome (normal rooms, huge monsters) where you have to either run the adventure as written fully in a Theatre of the Mind style, or (at minimum) double the dimensions of any room in which monsters are faced so that there is actually room to maneuver. While I call it "huge monster" it is actually more common that it comes up in a room that is simply packed full of monsters - the best example I can give is 9 trolls in a building that is 30' x 30'
And while the plot of each individual section of the super-arc can be a bit shaky, the plot across the whole is better - and of course I get to tweak it all to high heaven while adapting to make it better.
What attracts me to DCC is that it's a reboot of the old school with (hopefully) new school fixes, especially as regards coherency and story line. I'm personally hoping a few of the newer published modules will replicate that old school feel without the old school weaknesses.
Coherency and story line are definitely made much more solid by the style that DCC encourages - it's easy to string unrelated episodes together and toss in the few bits needed to make those episodes, in hindsight, seem more related.
As for a reboot of the old school... I am more of the opinion that DCC is the epitome of new school, since despite mechanical similarities it is the first game to say "we don't have to do things the way they have always been done," and actually mean it.