Best calculator for the working engineer

[Ron Ross]

Well, for the PE exam, you are limited to only a few select calculators and you already have the two best calculators available for that exam.
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I suggest you buy an Hp 50G to try, they are fairly cheap to buy via Amazon, new even. I am kind of partial to the Hp 48G line and they are also very cheap.
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For an EE, the Hp 42s is indeed a treasure. However, your spending $200 to find out that you think RPN is dated and unnecessary would certainly be a big waste of cash. An Hp 48G would give you a similar experience with a calculator of similar capability for about $50. If you feel that the Hp 48G is GREAT!, then consider splurging (or hunting) for the much smaller and portable Hp 42s (and knowing that you will like it, or simply "meh, I have a 48G and its okay").
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The Hp 48G has the exact same lower portion keyboard (and keyboard construction) as the Hp 42s, aside from RPL vs RPN (but you would get that comparison from the Hp 48G vs the Hp 35s anyway.