Yeah I think you're right - moving from mechanical to SSD made more difference in perceived speed than more/better RAM and faster CPU. Boot times are for sure a happy thing of the past, even opening up programs like Photoshop used to take long enough for me to alt-tab into the web browser for a bit while it started up, whereas now it's instant.
I've recently switched from 8GB MBA to 16GB MBP and to be honest, I'm not sure I've noticed any more speed above what's to be expected from any brand new machine before it gets bogged down with shit. My MBA used to be able to handle multiple big programs running in the background - 2 of the Adobe suite + Chrome + small stuff, so I haven't felt much use for the extra juice day-to-day, though I imagine the RAM is useful for video editing etc.
I've recently switched from 8GB MBA to 16GB MBP and to be honest, I'm not sure I've noticed any more speed above what's to be expected from any brand new machine before it gets bogged down with shit. My MBA used to be able to handle multiple big programs running in the background - 2 of the Adobe suite + Chrome + small stuff, so I haven't felt much use for the extra juice day-to-day, though I imagine the RAM is useful for video editing etc.