Hard call is right.
I've already got an AxeFX2 in a rack and all the trimmings it uses (MFC101 controller, Matrix Power amp, expression pedals etc) it's still enough to keep me satisfied and suppress (most of) the desire for an AxeFX3 tempting as it is. But I'm seriously considering getting the FM3 as well. Part curiousity/desire to use the latest firmware but also practical for slimming down the load for live use. I'm sure it could replace my AxeFX2 for home use too ... but I'm bad about letting old friends go!
Any 'live use' presets I've ever set up on the AxeFX2 will be easily reproductible on the FM3 and the lack of having a second amp block (which I used on the AF2 to switch between a clean amp and gainy amp via scenes) is not a problem now with the FM3 having channels to do the same thing.
If however I'd not already owned the AxeFX2 and this was my first foray into the Fractal gear I'm sure I'd be sorely tempted to aim high and go for the AxeFX3 over the FM3 ..... simply because 'more' would seem better. I suppose, logically thinking, it actually is 'better' because of the extra functionality, however the engine providing the tones of the 2 units is exactly the same .... and the AxeFX3 is considerably more expensive (and might require buying a midi foot controller too depending on your needs).
For your use in your home studio only I think the FM3 would be absolutely fine - if it's main use is for recording then you'll likely be already be planning to double track, layer, add some external post recording FX via your favourite plugins etc. so you'll never be stuck ....... you'd very likely be doing the exact same thing with the AxeFX as well!
I think it's only natural you're probably always going to wonder if you'd have been better to go with the big brother simply because it exists. But either unit will be
very competent when it comes to convenient, real time editable and authentic sounding recording.
As for the 'really nice presets' you mention, I know there's a lot of AxeFX3 made presets with loads of blocks taking the CPU over the FM3 limit out there as well which will be added temptations - but not all third party presets are going to sound like they do on YT etc. Some might work well straight away for you but most will need a bit of a tweak here and there to suit your own monitoring, guitar and playing style. There are a good few native FM3 designed ones too though.
I'm not trying to say all third party presets are completely useless or anything but the good ones are certainly good starting points ... you will probably need to do 'something' to them to make them 'yours' so don't base your decision on what you hear on YT entirely as plug'n'play.
So my recommendation would be FM3 -
- It's a cheaper option for you to introduce yourself to the Fractal modelling experience.
- It may have some things missing that the AxeFX3 has but I doubt they'd make much difference to the average home player.
- It has footswitches built in with plenty of layouts available to set up and access different things but it's also expandable using either a FC controller or a midi controller by another manufacturer.
- If you like what you hear and feel the need to change to the AxeFX3 down the line you should have no difficulty selling the FM3 on.