Some powers have extra or different benefits depending on which class features you pick. For the purposes of this question I will refer to the power which prompted it, the Swordmage's level 3 Encounter power Dual Lightning Strike, which can be found in Arcane Power.
Dual Lightning Strike's Effect reads:
Effect: You teleport 5 squares and make a secondary attack.
Which is followed by this special benefit:
Aegis of Assault: The number of squares you teleport equals 4 + your Strength modifier.
I'm making a hybrid Psion-Swordmage who has 10 Strength and Melee Training (Int), so his Strength modifier is zero. He has the Aegis of Assault, so can I choose to teleport 5, or do I have to use the Aegis of Assault benefit and teleport only 4?
I realize that some potentially questionable design decisions were made in creating this character, such as an Assault swordmage with 10 Strength or the combination of Assault and a controller. Please rest assured that these decisions were made due to thematic reasons and focus your answers on the actual question.
A good answer will have rationale one way or another. A reference to a rules book, official FAQ, errata, interview with a game designer, or something along those lines would be best.
Note that the near the beginning of the Swordmage Powers section in the Forgotten Realms Player's Guide it says:
Some swordmage powers include a line titled "Aegis of Assault" or "Aegis of Shielding." You gain this extra benefit only if you selected the aegis of assault or aegis of shielding power, respectively.
It seems odd that I would be worse at teleporting because I have the Aegis of Assault, but the way I read that last quote it's hard to say. It doesn't explicitly say that I must gain the benefit, just that I only gain it if I choose the right Aegis. A 'must' or 'may' in that sentence would really help.
Now, let's assume that I can decide to ignore the extra benefit and teleport 5, whether because that's a RAW interpretation or because my DM house-ruled it. If my Strength increases in the future and I manage to get a +2 modifier, can I then change my mind and start using the benefit, or do you think that that's a permanent choice one would make when gaining the power?