Perhaps the best in the X-Com series, it focuses on combat. There is no 'buying' or 'selling' anything (though having extra to trade is helpful). You are limited in the number of characters and they are not imbued with individual statistics (perhaps the biggest drawback IMO). You can also build an unlimited number of drones but they lack some capabilities. On the plus side you have to collect prisoners and artifacts to further your research. Personnel decisions are important since you are limited in the number of humans (and aliens!) you have available. Indeed many of your personnel can either work in the lab or workshop or fight. [Some people have two of the three abilities [soldier, researcher, technician]. Though initially very challenging by the end of the game if you are careful you can finish the entire game with all the beginning characters still alive and actually go through entire missions (even the final one) with no casualties being taken at all. Diplomacy is limited but with care and luck you can have both Reticulans & Martians be on your team. One of my favorite games. And for combat the best in the X-Com series [I am not counting X-Com2 as I still can't get it to work in Linux.] There are mods available such as a rebalance mod [https://www.strategycore.co.uk/files/total-rebalance-modification-v2.03.1-ufo-al/].