Well, I've been a judge at IPMS regionals, and I've been judged at both IPMS and AAMPS-style contests and in my opinion, there are some huge problems with IPMS judging, so much so that I'm pretty much done with IPMS style contests. In short, IPMS judging pretty much sucks--not the people, but the methodology. AAMPS-style judging--where each and every model is judged against itself and an "ideal"standard, is the best method of judging.
When judging IPMS contests, yes, it's sad but true that very often the "senior" member of a judging team is overly deferred-to, much of it human nature because the designated judges are usually judging with one or more volunteers who just wind up being mostly "yes men", or who don't really understand the peculiar points of IPMS judging, and are easily intimidated by a knowledgeable, recognized judge who carries a bit of gravitas by virtue of his title alone. I also think that nobody wants to get on the bad side of a judge by disagreeing too passionately, for obvious reasons. In my experience, judges quickly peruse a category, then pick the "obvious" best ones, then go about looking for reasons to disqualify one vs the other for first place. Again--it's more of a process of "DIS-qualifiaction" than to reward what is good about a model. Once two or more models are deemed possible winnners, usually one THEN does the discussion turn to "Well THIS is very nicely done here; THAT looks like it took a lot of effort". The shame is, if four models are fabulous, with very minor, minor points of distinction between them, one of those beautiful models is going to be off the "podium" so to speak.
But another thing that hurts IPMS is that I believe that there is a firm, undeniable bias against today's new "weathered" style. Let's be honest--a lot of IPMS judges are older guys who grew up in the traditional style of modeling with only a wash and drybrush to "weather" a model, and a lot of them seem to vote against heavily-weathered models no matter how well they're done. I won't deny that I have a heavy bias and sensitivity here, but when you read some forum opinions about what's "realistic" vs "artistic", there are people out there who will not agree, under any circumstances, that any more weathering than THEY think is appropriate is "correct". I have seen some trult spectacular models be passed over for trophies by models that were plainly and truthfully, simply boring. I have read an opinion in the past that "IPMS rewards mediocrity", and while I won't say that I haven't seen some SPECTACULAR winners who MUCH deserved their First Place trophies, I've seen just as many First places which left me (and others in the room) shaking their heads in disbelief.
And that's another problem. The way that IPMS judges models---and this is an old and perennial complaint--it throws the baby out with the bathwater. In other words, you can build a show-stopping, popular-vote-winning stunner of a model, but if Judge A with his flash light, 6x magnifier and dental pick detects one 2mm seam that you missed on the bottom of an inner road wheel or something similarly insignificant "error" on the underside of a gorgeous model---you're toast. It's dis-considered for a trophy. But if you're lucky and careful enough to cross all of your modeling T's and dot all of your styrene I's, but put a bland, uninspiring finish with little creativity on your model, you COULD potentially take home a first. ESPECIALLY if there's only two or three in your class. And you could beat that stunning, stand-out model because of that tiny 2mm seam. And ironically, if you're lucky enough to have on one other entry in your class, your very-poorly built model with obvious, glaring flaws can take home a 2nd place! It's just infuriating and everyone in the room goes up to that guy and says "Your model was the best, man; you wuz robbed". But the results stand. A lot of guys go home pissed to the moon because of this, and I've been on both sides of the problem. Not going to deny my personal bias here, but I also have felt terrible for guys who were crushed that their obvious effort was beat by something very basic but so very "correct".
AMMPS judging takes each model, assesses it against an ideal, and then gives you points on or off, and tells you what you could improve. There's no allowance therefore for a poorly-done model taking a First when there's only one in a category, as I've seen so many times in IPMS. You get judged for what you got right AND wrong. In the end, I think a modeler walks away feeling respected and validated, recognized and appreciated for what they've entered, unlike so many IPMS contests where guys just stop entering because they just never place or feel recognized in any way.
I don't mean to criticize or demean any IPMS judge out there--I've been one myself. But they/I are just captives of the system, and every one of us is human, makes bad calls and mistakes, and has their own biases. It's not so much the people but the manner of judging that really is poorly designed and results in so much frustration. AAMPS-style judging admittedly takes much longer, but in the end, it's a much more satisfying contest to attend. and it's a shame that it's not adopted as the standard.