The AM4 honestly has very few shortcomings for the basic user. IMO its biggest issue is the lack of 4CM capability followed by missing pitch and multitap delay fx. But if you use it as an all-in-one, then those shortcomings become less of an issue.
What the basic user needs is something that replicates their typical pedalboard + amp signal chain in the virtual realm and is relatively easy to use. Part of the HX Stomps popularity besides its small form factor and lower cost has to be that it does just enough for most people.
FM3 to me is pretty much dead as a product after the AM4 release because it's bulky, and doesn't offer enough over the AM4. The main reason to go for the FM9 is the dual amp/cab features and more complex effects chains. But in Europe it costs over twice what the AM4 costs and you could buy a VP4 + AM4 or dual AM4 for less. Remember, the G66 pricing really sucks for us Europeans. We pay about 160 € / ~$189 more for the AM4 vs US retail price, and that's before VAT.
The AM4 has been a bit of a rugpull over new modelers because even though it has a more dated user interface, it's still streamlined enough that it's not annoying to work with. When it came out I wasn't convinced but now owning it, I have to admit I was wrong. It does just enough to take out the most annoying parts of the Fractal onboard UI experience that I no longer reach for the editor software.
While Helix Stadium is going to be even easier to use, it does come with a much bigger price tag (about 2x AM4 in EU) and is a less mature, and a bit larger product.
I guess when I gave up my tube amps, I also gave up on a custom pedal board about the same time. The idea was to simplify, lighten, and minimize the opportunity for anything to go wrong on stage.
The way I understand it, the AM4 has a noise gate/compressor at the start of the chain (reasonable since this is a very popular thing to want) 4 slots; however, 1 of those should be an amp .... so an amp and 3 effects, and an output EQ. It also looks like you can get a boost without using a slot, but I am not sure hot this might work. I agree with you that this combination covers the lions share of every signal chain. It definitely covers most everything I do.
YMMV indeed. I've found over the years that it's a rare case where I would have more than 1-3 fx on at once. I don't do the "drive A into drive B" stacking thing, hell I don't even use drive pedals most of the time since my amps are very capable.
Yep. Me too.
I have come to rely very heavily on my Band Helper interface though. Love having a setlist drive my guitar pedal setup just by switching to the next song in the set. Takes all of 5 minutes to create a new set in any order I want. Since I have a tablet on stage anyway to adjust my IEM mix (which I don't have to do much with or very often now that things are dialed in), having a setlist manager is a wonderful thing. I wouldn't give that up now (ever); however, even the AM4 has MIDI so I wouldn't have to.
So what my next rig selection comes down to in my case is good amp tones, good reverb, good delay, ability to quickly setup a particular tone on a patch, and MIDI control for setlist automation with 4 buttons or more. At this particular moment in time, it looks like I could have everything I need in an AM4 and buy a backup for the price of the Stadium.
Still, Stadium is a MUCH more powerful platform. With time, I think the tables will turn, but the fact is AM4 really did shake up the market IMO.