Both two you mentioned are about the same in SQ rating.
It comes down to what kind of signature you want.
FXT90 will be more aggressive, with punch bass, forward mids and sparkly (though not too sparkly) highs. Also, the timbre is the best from everthing I've ever heard (I never heard the FX700 though)
EPH-100 will be much more laid back, smooth, non-fatiguing. Still punch bass, mids not as forward as FXT90, and smoothed treble (not sparkly).