I use superglue for everything, even when it is not the best choice. I can't comment on the glues you have listed because I have not ever used them. I do hear good feedback about E6000 though.
Gluing the letters probably needs a decent glue because you are gluing foam to rubber and that rubber is both a complex 3D shape and textured. When these are on your feet, there is some range of movement. The biggest concern I have had in people stepping on the back of your shoes. My kid did it to my MAGs yesterday. People are either not aware they are in your space or they don't care.
Can't wait till my new mold is made and I will have almost RD accurate letters.
http://www.therpf.com/attachment.php?attachmentid=515885&d=1439782846
This is being machined up now.
NIKE = 18mm
MAG = 25mm