no date oyster perpetual vs explorer 1

[ismelllikepoop]

Dumb question, but what's the difference between an oyster perpetual and a 36mm explorer 1 besides a fluted bezel? Started looking at 36mm watches after hodinkee's recent article on datejusts, and noticed some of the watches are very similar to each other. Heck even the 3/6/9 air-king looks the same as an explorer except it's 34 mm, but is considered a different line. Anyways tried searching the forums but the search function here is hard for me to use.