Avogadro6: Vanilla JA2 is still excellent and can easily offer hundreds of hours of content; it can be a little overwhelming at first, but if you like the genre I'd say you can't go wrong with it. Then there's the 1.13 mod, which I think restores some cut content and introduces new features and weapons. I haven't tried yet, but the general consensus is that it's very good.
Wildfire: don't have it, but it seems to be more of a remake of JA2 than a real expansion, at least going by the reviews. I'm guessing JA2 +1.13 is considered superior though.
Unfinished Business: stay away from it. It's poorly balanced and incredibly frustrating. While JA2 is challenging but fair, UB puts you against an army of elite supersoldiers with inhuman reflexes, where it's extremely easy to lose your best people without even having the chance to react. I made it to the end, but only by savescumming a lot. Never again.
What? lol. No. I just finished replaying Unfinished Business. Loved it. While it does have definite issues (i.e. rooftop mercs can be unfairly shot at despite impossible angles from land-based enemies), it is challenging but definitely playable. I loved the additional mercs like Stogie and Gaston. Made playing the game that much better. Save scumming is part of the game unless you're an absolute pro. Part of the learning curve comes from replaying scenarios and learning better tactics.
Wildfire is way harder with newer weapons and redesigned interface. From what I've read, it's basically a community mod that was commercialized.
Play JA2 Vanilla first then try out Unfinished business. Then check out the other mods, 1.13, etc.
The other iterations of JA weren't the same. Back in Action was a disaster in my opinion. Nothing beats the JA2 experience.
