Last year they were available around the 1st of the year for $200 if you had a standard addition iZotope product. (A lot of the iZotope Standard products sell for $50 on sale) I've been waiting all year to see if that happens again.
Ozone and Neutron are wonderful. Izotope puts out tons of educational videos and the software has a lot of ready made presets. That's great. But when you look closely at the presets, you'll notice that most of them are not geared toward orchestral music. I worked with Ozone/Neutron exclusively for about year. I learned a lot, but not enough. That's my fault. For me, some of the modules were overwhelming and confusing.
I kept seeing that many users love FabFilter, so earlier this year I downloaded the Q2 demo. While it doesn't have has many presets as Izotope, this FF plugin was much more intuitive for me. I bought it and have been adding other FF plugins over the past several months. I also added the compressor, multi-band compressor and limiter. At this point in time, I prefer them to Izotope.
My impression is that Izotope was built for engineers and FF was built for musicians.
They're all great products. As stated above, try out the demos yourself and see what feels right for you. Watch as many videos as you can, there's a lot of them.
I agree that the *presets* aren't geared toward orchestral, but they can still give you a good starting point and you can tweak it however you will, and the tools provided can be wonderful for orchestral music. Also most of this forum is full of hybrid, trailer music, film and game music, etc and I think the bundle works well for that type of higher impact mastering. I second the suggestion to try the free trial.
I've used almost all the fab filters and I have the Izotope Music Production bundle 2.
Having used both, I don't think either option would be a bad choice. You could flip a coin and just go with one and be very happy for years digging deeper into the craft they facilitate. I massively prefer Izotope though, let me break down why.
Presets: I have no use for them, just not useful for me, I typically know where I want to go in a mix/master and using presets would just be clicking around for something close to what I would then modify the hell out of anyways. I never had that phase of using presets when I started, I just suffered through having crapy mixes for years as I learned how to mix and master. So this for me is a nonstarter, if that matters a lot then know neither is geared towards mixing orchestral music because that's only a small part in the whole of the mixing world. But the Saturn saturation plugin by fab is one exception that has some great presets I don't mind just clicking through and seeing is something interesting comes out of it.
Interface: with the exception of of the EQ (which I still sometimes use) I find fab filter less pleasing to use, especially the (C2?) compressor. I find that thing clunky as hell and its just not set up in a way I enjoy. A couple generations back I would of said fab was more pleasing to look at, but I really like the look of the new generation of Izotope products and I think the layouts are fantastic. They flow the way I want my tools to flow.
Interaction: Fab filter products work like most other plugins in this regard. Having Neutron talk to itself and having all sorts of nice interactions like boosting on eq and having another cut some space in the same place, or having a boost be able to follow a sound as it moves between a couple frequencies are amazing features.
Learning curve/depth: Fab filter is probably much easier to open up their stuff and just tweak things and go, Izotope was much more intimidating and I had to very slowly go through each product to get a decent understanding of them (and to be honest I'm still after years going "holy shit, I had no idea this could be done") I prefer depth and I tend to purchase things looking towards if I will still be getting something new out of it years later. Izotope stuff I feel has much more depth, but most of mixing is just craft, so again, if you find fab filter easier and just work on your mixing abilities then you'll keep seeing better results either way.
Those are my two cents.
Try out some demos, see what feels most intuitive and also look towards what has the most growth potential vs. how much work that will take and see what makes sense for you.
...Learning curve/depth: Fab filter is probably much easier to open up their stuff and just tweak things and go, Izotope was much more intimidating and I had to very slowly go through each product to get a decent understanding of them (and to be honest I'm still after years going "holy shit, I had no idea this could be done") I prefer depth and I tend to purchase things looking towards if I will still be getting something new out of it years later. Izotope stuff I feel has much more depth, but most of mixing is just craft, so again, if you find fab filter easier and just work on your mixing abilities then you'll keep seeing better results either way...
To some degree why I ended up with FF FX Bundle. FF was a breeze to work with and provided exactly what I needed as a writer/musician. The Izotope Bundle was probably a bit overkill and beyond the scope of my work.
If you're just beginning to mix, stick with the basic plugins that came with your DAW.
Spend money on new ones when you are experienced enough to know what needs to be done by listening to the track and having an idea what should be done (or not done) to improve it in the mix.
Learning how and when to use these tools only comes with practice.
Don't get me wrong, iZotope makes awesome tools, but thinking that buying them will make your results sound better is marketing not fact.