Detective Conan is too repetitive in its plot, though of course there are some progress but it feels like they are stuck in the same problem with a long period of time.
I suggest reading One Piece first.
The worldbuilding and power system is so well written and you wont get bored at all
I read both and have done so for 20+ years. Whether I recommend one or the other depends on what you're looking for. Do you want a story that is mostly stand alone cases where you can go to sleep and not pull an all nighter to finish the arc? Go for detective conan. Do you want something that you will look forward to and that has 50+ chapters per arc? One piece is your answer. Both have some repetitive elements because you can't have over 1000 chapters of unique material, some things are bound to have patterns but they are both enjoyable.
I would recommend that you alternate and read one this week and the other one the following week and so on and so forth
What I can recommend you regarding Detective Conan is to find a website that shows you what anime episodes are important for the plot and watch them in 1.5-2x speed. I did that and caught up pretty quickly to the current chapters since a lot are filler cases.
And from time to time I like to (re-)watch some favorite episodes or new ones with characters I like.
I'm pretty sure there are similar websites for the one piece anime as well to shorten the the watch time and then hop on to the manga (or you could wait for the Netflix one piece anime to come out. I heard they compress the arcs into a lot less episodes than the toei anime). But since you can't skip any chapters/episodes in one piece that would be a bigger commitment. But also more rewarding if you stick to the end and experience the end with all the other fans.
Detective Conan all the way! If you want to skip the fillers - but Fillers is Life in DC - you can just check detectiveconanworld.com/wiki/ to find out the manga canon for anime or the Black Org arc for manga.
I restarted watching fr ep 1 about 10 years ago while I was traveling extensively for work, didn't skip the non-manga episodes and caught up in about a year (they were in the 600s/700s I think). I live detective mystery so it was fun to watch. I reread the manga around that time as well.
There’s almost the same number of chapters for this as One Piece. I started both, like 15+ years ago, but then quit them well before the 800 chapter point… now I’m considering restarting, which will require a reread… I don’t have it in my to commit to both right now.
Which one should I pick up first? Opinions? Reasons?