I have an MSO1074Z-S (uphacked, I was an early adopter, and had to take the lid off and use a JTAG debugger). I also have a couple of the $100 60MHz FY-6900 plus a Saleae.
First, the Saleae hardly ever gets used, indeed I can't remember the last time I used it. It's only if I need to capture a particularly long trace that I used it. The main reason is that with an MSO (and traditional logic analysers) you set up triggers rather than relying on huge memory and post processing. In my experience, the trigger options of the Saleae are incredibly limited. Simply put, you just use the tools in a different way: how do you think we all managed before Saleae?
Secondly, the $100 function generators are OK for the price, particularly as they go to 24Vpp. Downsides of the MSO1074Z-S signal generator are that it has limited amplitude (5Vpp into Hi-Z), relatively speaking the AWG can be a bit of a fight to use with the UI, and irritatingly the BNC jacks are on the back. On the plus side, unlike many other scopes with integrated signal generators, it is a dual unit. Having the unit integrated into the scope itself is great for field use, and that's precisely what I use the MSO1074Z-S for. Functionally speaking, only the amplitude restriction has been a practical limitation for my use cases. You can phase offset both channels too, so you can use it to create things like quadrature oscillators.
Finally, I'll also add some practical notes about how the LA integrates in the MSO1074Z-S. The key benefit is that both analogue and digital signals are time correlated, something that would be fiddly with a separate scope and LA. My work is very much mixed signal in the area of digital communications, so this is quite an important facet. Each batch of eight digital signals is used at the expense of one analogue port, so you can operate the scope as 4+0, 3+8 or 2+16 channels.
Digital channel usage also affects sample rate, so running only 8 LA channels and no analogue channels (and no analogue trigger) you get an LA sample rate of 1GSa/s, which is clearly immensely better than any Saleae. Add an analogue channel or trigger, or increase to 16 LA channels and the sample rate goes down to 500MSa/s. If you run more channels, it goes down to 250MSa/s.
I've found that the digital connector on the scope can collect dust and the connection becomes intermittent, so keep that in mind.
The screen very quickly becomes cluttered when you add digital channels.
Just as with the analogue channels, the decode is limited to what's displayed. Using trigger functionality is often key to using decode effectively.
I don't use any PC based software with the scope, so I can't comment on that aspect.
What I would say is that for a field scope, if an Analogue Discovery won't cut it due to its own limitations, an MSO1074Z-S is a very worthy upgrade. For $350, what are you waiting for?