As has been stated a lot of times before, you can't "be" 50/50. Your functional order would be either Fi-Se-Ni-Te or Fi-Ne-Si-Te, not because you "can see it both ways", but from the point of what's driving your default behavior.
Yes, I agree, that on the paper, ISFP and INFP seem to be pretty similar in theoretical action, but having grown up with an INFP mother and an ISFP sister, I can assure you that they are driven by very different motives and with very different goals.
Read up on Se and Ne in
this most excellent post about functions and how they work. Having Se or Ne as your second function, means you use one of them as a means for input of data to feed your primary function, Fi.