We used PS with our older son (OS wasn't created yet) up until he was out of diapers. We never needed larger than a M, which was awesome. After prefolds/covers in the early days, the M PS was all he needed.
Now we use both PS and OS (along with a mix of other dipes) with our youngest and I like both. I love that the OS has the replaceable elastic. My initial stash, after being used by 2 kids and being stored for a while, ended up with shot elastic and I couldn't use them (still need to get those to a mama who can sew!). I like the idea of being able to replace the elastic and get much more use out of the OS. As for fit, we like them both - have no complaints.
Washing routine is the same.
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