I notice that some do 3/5/1 instead of 5/3/1. Is there a reason?
If you push yourself hard it may be beneficial to do the middle week lighter (85% top set, no PRs etc). Some programs have built in 3/5/1 order.
In the grand scale it does not terribly matter which one you’ll use.
As mentioned in the Forever book, sometimes the 3/5/1 has advantages (as Rattus pointed out). It all depends on how you program your training.