The Explorer II has a 24 hour hand that allows you to tell time in two different time zones simultaneously. The outer bezel is fixed with the 24 hour markings. The Date submariner does not feature this but does have a rotating bezel that can be used to time a variety of things. Both movements are similar in accuracy and function other than the 24 hour hand. The sub is more common though the explorer II has gained great popularity over the last 10 years or so. The sub probably still holds its value slightly better and might be slightly easier to sell later on. It is a toss up. I had the explorer II and enjoyed it very much. It was very accurate and reliable. The cases are nearly identical in size and weight. The bracelet on the sub is the fliplock while I believe the Explorer II still comes with the standard clasp. They are both excellent watches and you would likely be happy with either of them.

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