My vote for Nf6.


Nf6: 8 votes (dre1982, hermesesus, Morecoin Freeman, XMRpromotions, galdur, languagehasmeaning, boolberry, jjacob)
b5: 1 vote (Hueristic)

Nxe4: 2 vote (Morecoin Freeman,Hueristic)

Nxe4: 2 votes (Morecoin Freeman,Hueristic)
Be7: 2 votes (galdur, boolberry)

If I understand well, we have basically the choice between:

• playing with caution: Closed Defence (5...Be7)
• or being more agressive: Open Defence (5...Nxe4)

Apparently, the problem with the Open Defence is the Karpov's move, 9.Nbd2, which limits Black's options.
http://www.chessgames.com/perl/explorer?node=37411&move=9.5&moves=e4.e5.Nf3.Nc6.Bb5.a6.Ba4.Nf6.O-O.Nxe4.d4.b5.Bb3.d5.dxe5.Be6.Nbd2&nodes=21720.21721.21722.21723.21724.21725.21726.34841.34842.34843.34844.34845.34846.34847.34848.34849.37411

(Correct me if I'm wrong)

Thus, I vote for 5...Be7.

Be7: 3 votes (galdur, boolberry, hermesesus)
Nxe4: 2 votes (Morecoin Freeman, Hueristic)

I would tend to agree the that the open defense is more aggressive but there are many exceptions. There are some very boring and drawish lines within the open defense and aggressive possibilities in the closed.  

The line you mentioned is one possibility that could limit our options in that open variation. However white has the ability to limit our options after Be7 too. For example white could stop us from playing the Marshall attack with 8.a4:
www.chessgames.com/perl/explorer?node=1832213&move=8.5&moves=e4.e5.Nf3.Nc6.Bb5.a6.Ba4.Nf6.O-O.Be7.Re1.b5.Bb3.O-O.a4

This early in the game both sides have multiple plans to choose from with no clear consensus about which one is "best".  Since we all have different preferences it is unlikely that everyone will agree on the best plan. As someone else pointed out there are actually other options besides Bxe7 and Nxe4.