I'm thinking of the knob assignments (KB0-KB9) in the context of the PitchFactor as I write this. I use an expression pedal, 3-way aux switches, and various MIDI devices to control the PF.
With the variety of the algorithms available, global aux switch settings will rarely line up in a useful way across presets. If the MIN VAL and MAX VAL limits are utilized, it can become even more problematic. For example, KB8 & KB9 with control feedback in a Diatonic preset, and control intervals in a Quadravox algo. Then kick in a Synthonizer preset, and … you get the idea.
I would describe an expression pedal input like I would a fretboard glide or string bend. Smooth, "analog", and hitting every intermediate value. Using the aux switches is more like a hammer-on, or pulloff. Discrete, "digital" (forgive the pun), with an immediate "snap" between values. Both approaches have their strong points.
Again in the Pitchfactor, I find a lot of uses for that immediate snap-to-value. Simulated chord changes / pedal steel, instant key / interval changes, instantaneous shift in delay values, jumping among Harpeggiator patterns, etc. In these situations, gliding through several "in-between" values throws off the timing and desired effect.
Consider assigning multiple parameters to each available aux switch. (I know, I know. The manual states that " doing so is likely to cause confusion and is not recommended."). Start at the lower parameters, toward KB0, and work up sequentially to KB9. The highest parameter programmed is the one that will be displayed when you step on the multi-assigned aux switch.
Some parameters may have 7 intermediate values between "targets"; other two, or five. If an expression pedal is used, a halfway position between heel & toe will be different for each assigned parameter. Sometimes, that's a good thing (morphing). Other times, it may be more appropriate to jump all assignments straight to the destination values (chord changes).
All that said, I'm not a diehard advocate of per-preset assignments, especially if it burns up precious memory that can be utilized elsewhere. My workaround has been to program companion presets in a MIDI switch/pedalboard, and send CC messages to accomplish the same goals.
Of course, if Eventide doesn't have another use for those "extra" 28 slots that are accessible via program changes, but not the front panel … 
