First I would say in your list, some of the software is quite distinct, but with lots of overlap. I would classify them as:
PokerStove + Equilab: These are equity calculators. There's no real reason to use pokerstove over equilab - equilab it does everything pokerstove does + a lot more. They are both straight equity calculators, with equilab adding in some analysis tools like the next street analysis, flop texture analysis etc.
Flopzilla: board texture analysis. See how well a range hits a board. I think it now also has turn and river support as well.
Holdem Viewer: this is a different beast, and it's real job is constructing preflop ranges.
Stox/Cardrunners EV: this is a unique tool that is an open-ended scenario calculator, where you can construct branching decision trees and run simulations over it. It's a very special product.
OddsOracle: I will preface this by saying i haven't really used this much in my normal study flow since it's been released, but it looks like a very strong equity calculator product. It's does everything a normal equity calculator can do, with the addition of supporting non-holdem games, and it's own custom range description language and query language. You can also set up combinatorial 'questions' (how often will this range make a flush etc) which was a bit fiddly when i tried, but the open-endedness is pretty powerful, and it's toolset is unique for non-holdem games.
Combonator: So now we get to combonator. Firstly, Combonator presents itself in a very different paradigm than any of the tools above: Everything is centered around the hand grid, where you can assign hand combinations into multiple groups. As you update the hand-grid combination counts and equity calculations update instantly. Combinations can be removed from the grid as you proceed through the streets of the hand. This way of working is quite different to any other program, and feels to me much more intuitive. I believe its the only tool that has a full undo/redo history as well, which is very useful to rollback changes and try different things.
It's combinatorial support is fairly unique, allowing you to do stuff like construct balanced flop checkraise ranges, see the bottom x% of your range, see how a turn card effects a range of hands etc, is rather unique to Combonator - i'm sure it can be replicated in tools like Odds Oracle, but in Combonator these things are literally a click or two away. I would recommend watching the intro video on combonator.com which shows how Combonator can keep up with your thought process
But ultimately, there is
a lot of overlap with other tools to the actual answers you get - you might just find Combonator a lot faster and more intuitive to get the results. With combonator v1.6 you can:
- Do preflop range vs range calculators (HU only), with equities processed instantly as you manipulate the hand grid. Combonator has many advanced preflop range selection tools like custom rankings, fast grid selection, saved ranges, suit selection etc. It does not yet have preflop hand weighting.
- Do range construction preflop like Hold'em Viewer (the graphs of HV cannot be done in combonator yet, but otherwise i believe Combonator replicates the features of HV.
- Do postflop hand vs range calculations (HU only) like equity calculators, but in combonator these work on the fly as you manipulate a range, and equities are shown for all grouped hands, vs entire range, and for individual groups all at the same time.
- Do board texture analysis like flopzilla, with teh ability to instantly assign groups into ranges.