I have never had to take my belt and shoes off to catch a train in Europe or the USA but have been close to strip searched at airports.
I fly regularly, I have never had to take my shoes off going through airport security locally, or internationally, for domestic or international flights, taking a belt off? Big deal, where appropriate (or more likely when I all too well infrequently remember to) I just wear pants/shorts that don't require a belt, but having to take your belt off really is an insignificant inconvenience. I am more annoyed by needing to remove my watch, but that's only because of it's value - and much of that is sentimental.
Don't forget to add to the air travel time the time to get to the airport and the need to wait around for so long and go through security.
Do you by extension remember to add the time taken to get to APT and then wait around for the Overland to depart? For me, there is likely negligible difference between traveling from my home to YPAD or APT.
Waiting around for so long? For a business trip to Melbourne (the market you're pitching to) I get to the airport maybe (very likely less than) an hour pre flight, I am taking a carry on case at most. My last international trip even excessive amounts of luggage to check I got to YPAD only 2 and 1/4 hours pre flight, which included not only going through domestic security, but international security, the 'stand in here while it spins around looking for explosives' thingo, immigration control and duty free.
Our last trip (before Corona ruined everything) just happened to be to Sydney. Qantas bent the aircraft destined to operate our flight both
ways, which if flying to Melbourne would have seen us still beat the train by a solid 8 hours. Our delay included needing to leave air side, collect luggage which was already on board the aircraft pre cancellation from the carousel downstairs, get re booked, recheck luggage and get back through security (taking my belt and watch off again), then 'finding' Coopers' which wasn't where it usually was, ordering a toasted sanga and beer - and that was only to use my $15 Qantas 'inconvenience voucher'.
Returning home, our flight ex Sydney had the aircraft grounded before it departed to fly to YSSY meaning that Qantas actually had some notice of the cancellation and they sent me a text and email before
we had even checked out of the hotel, advising me of alternate options. I chose to be booked onto a night flight rather than an earlier flight meaning we experienced a delay of more like twelve hours when it could have been closer to two - but it gave us a bonus day to meet another friend from Manchester who happened to be in Sydney for work for lunch and then again for dinner, and do some further shopping.
In both cases, were these flight to/from Melbourne by time in motion, total time, time including security, angular distance covered by the planet whilst I travel from my home to my hotel, by any measure, it doesn't matter, aviation even with two delays wins easily, even if I doubled the minimum delays, or tripled the delays, aviation still results in less time - it's just not even vaguely close, even if you squint and look at it really hard, there's always that order of magnitude difference.
I posted quite some time back, the Overland isn't 'dying' because of marketing, timetabling or anything else under the service operator's scope of input. It's effectively dead because WWII necessitated us learning to build decent sized, decent range, decent reliability aircraft. Dare I say it, blame old mate Adolf, or the terms signed to at Palace of Versailles, or whatever your chosen view of the triggers to WWII were, but marketing and timetabling of the Overland are not the problem.