I've owned both and compared them head-to-head (FW17.04 and FW2.8, FAS & KPA respectively through a Matrix GT1000FX & a pair of passive CLRs).
When running each as follows: Guitar->wireless->modeler->Matrix->CLRs, I noticed the following:
Feel: toss up. I couldn't distinguish one having a more amp-like feel over the other. That's for cleans, crunch, high gain, whatever you threw at them. Both responded very well, both cleaned up well with the vol on my guitar.
Tone: slight edge to FAS (also for the full range from clean to searing). Here's why: I can dial in a shit tone on my AxeFx and it'll sound like shit. I can also dial in outstanding tones and they will sound outstanding. That's the FAS. With the KPA, it's all about the profiles. Shitty profiles are beyond worthless. The great ones are exactly that... but you have to buy the great ones (there are some very good freebies, but they're rare. It's exceedingly rare that the great free profiles also work with your particular guitar). Then you have to make them work in YOUR mix. There are those out there who, for a fee, will build your dream tone for the KPA... but you're here, gun-shy about shipping costs, which leads me to believe that may be a problem (custom built tones can run into the $900 ballpark or higher).
Price: edge KPA. It's cheaper. Period. But keep in mind that their "free shipping" is built into the cost of the unit, they're just not telling you that. Business/Marketing 101. The phrase "you get what you pay for" pops up in my head after owning both... grain of salt I guess.
Resale value: edge FAS. Both are very desirable units and don't last long on the used market, but AxeFxII's tend to go for a higher percentage of their retail value on the used market. As another forum member recently put it, "they're as close to liquid cash as gear gets," or something to that effect. I'll leave it to you to decide why.
Foot controllers: neither. I know it must be pissing Cliff off for me to say this -repeatedly - but there are cheaper and equally functional alternatives on the market. That goes for both FAS & KPA. I won't go into detail here. PM me if you're really interested.
Effects: clear FAS victory. I'm talking about quality here. Yes, the KPA has the "true" pitch shifting and formant wah... TBH the pitch effect is cool. The formant effect is virtually useless in the real world. When it comes to the nuts & bolts effects that nearly everyone uses at some point (reverb. delay. OD. etc.), the FAS effects are light years ahead of what the KPA offers, despite all the perpetual complaining of "the [effect block] doesn't sound exactly like my [pedal] when I've got dying Malasian batteries" you'll see in wish list threads around here. The truth is, FAS effects are pretty goddamned spectacular. I've even put some of them head-to-head with Strymon effects (Timeline/El Cap, BlueSky, Brig.) and some vintage & vintag-y analogs. The FAS isn't always the best for effects, but they're far better than what the KPA has... but effects are not a big deal for you, so take it for what it's worth in your situation.
Routing: landslide FAS victory. Dream it. Build it. With a flexible PA, you can literally set up for any conceivable routing needs, either in the grid or through external hardware. This of course also applies to effect placement. The KPA is much more flexible than most rigs, but still nowhere near the level that FAS takes it to.
Learning curve: clear KPA win. This might not be the case for you, being a studio cat, chances are good you have the knowledge to dial in a good tone fairly quickly, and with the AxeEdit software (no KPA equivalent... RM, but just to preview profiles) that should be easy. That said, there's a lot more under the hood with an AxeFxII. KPA is simple: load a profile. It sucks? Then load another one. I'm biased, but I look at it like I look at buying a new Camero... who the Hell buys a Camero that's automatic? Same idea.
Misc.: wash. Yup, FAS is 1U smaller. Flip side to that coin, you can get a 1U PA with the FAS, or a powered KPA which is still 3U... kinda' reverses the check block in the price column to do so, depending entirely on what PA you want to use.
Specific to you: I read through your OP a few times, and the only real question mark for me was why you're so hellbent on the RK & Egnater module (which, BTW, are the equivlent of swapping tonestacks - a FAS capability - and a portion of the initial gain stage, not entire preamps) tones. If you've nailed tones you love, high five, either profile them with the KPA or tonematch in the FAS and call it a day... but having played both amps for a decent period, I have to believe (and for my tastes I KNOW) there's better tones out there. For either unit. I guess my question is why are you looking here and not sticking to what you've already got?
Anyhow, people tend to get upset when I say this, but it's the truth... I don't care what you use. It doesn't affect me in the least. I'm just trying to be impartial and give you the info you're looking for. But, like I mentioned a few times before, I'm biased, because I sold off my KPA (to my neighbor who is also a veteran player and a studio cat with a good ear for tone) and kept my FAS. I will say though, I didn't do that so that I could say as much to you here and now. I did it because it was the better unit for my needs and gave me the sounds I was after.
...grains of salt.
...get a good playback system for either one.