Chaos in Cairo (CiC) and .45 Adventures (45A) are both pulp skirmish rules aimed at similar periods.
Chaos in Cairo
CiC is focused on battles in the streets of Cairo between four different types of warbands. It features archaeologists and mummies, both of which are pretty much self-explanatory. Then there are the Servants of Set, evil humans that are often twisted caricatures of humanity as they have meddled with That Which Man Was Not Meant To Know. Finally there are the Swords of Ra, a group of Bedouin-like warriors, who seek to prevent the secret knowledge of ancient Egypt from being taken by anyone (think the black-clad types that fight the Set warriors in The Mummy Returns). Each warband consists of characters (the heroes) and henchmen (groups of lesser humans). You can also recruit special characters, some of which are unique. Typically a warband consist of around 5 - 10 characters and henchmen.
The system uses goal rolls to determine success or failure. Each character has stats and skills that tell you how many dice to roll when testing. Each roll of 4+ is a success (a goal). You are either rolling to beat a task number, or another character's goals. In the former case, you succeed by scoring as many goals as the task number or more. In the latter case, the player with the most goals wins. The system is simple and elegant, using around 3 to 7 d6s for each roll. This system is used for everything from combat to jumping ravines.
Speaking of combat, characters in CiC do not get killed directly in combat. They can be knocked out once they run out of hits, in which case a doctor or character with medical skills can revive them. Once knocked out, you can administer the coup de grace to them, which renders them permanently out of the fight. Character death is dealt with in the post-battle phase. You roll to see what effect being knocked out has on a character. There are penalties on this roll if they have suffered a coup de grace, so it is more likely that they will die permanently in this case. This is only really relevant to the campaign game.
The game is geared towards campaign play and warbands are designed with that in mind. You can easily play one-off games if you want by agreeing how much to spend on each warband and rolling for or deciding on a scenario, but some of the skills that characters have are more suited to campaign play. Six scenarios are provided in the rules and each has three sub-plots that can be used with it. In campaign play you roll for scenario and sub-plot, play the game, roll to see the effect of being knocked out after the battle and pay for the upkeep of your warband. Characters can gain experience and become better or they can die and be lost permanently. You can earn more money and recruit new characters or henchmen during this phase.
Chaos in Cairo provides all the rules you need to get started with a campaign. The scenarios are given a little flavour by the sub-plots but are fairly generic. On the other hand, preparation is kept to a minimum, which gives you more time for playing.
45A is a rules set of another colour. Characters in 45A are graded according to their skill level. There are 3 grades of character, with Grade 1 characters being the spear-carriers. Grade 2 characters are the sidekicks, while Grade 3 characters are the heroes. Each character has skills, as with CiC and a set of stats but there the resemblance ends. Characters in 45A have hit locations, unlike CiC, and each hit on a location degrades the stats associated with that location. Thus, head hits reduce your Brains score. This means that characters slowly become less able as they take damage, until they are knocked out, while in CiC, characters are at full ability until they are knocked out. Typically, you will field 3-6 characters in 45A.
Instead of a handful of d6s, 45A uses 1d10 to resolve tasks. You are either trying to beat a standard target number of 10 or your opponent's die roll. You add your stat and skills to the 1d10 roll to see if you succeed.
45A generally uses more detailed scenarios than CiC. Instead of generic scenarios, the rules include a number of more detailed and specific scenarios. This really points up the major difference between the two rules sets. CiC encourages a more generic style of play, while 45A encourages you to write and develop scenarios that are suited to the characters you have created. The basic 45A rules do not include campaign rules, but these do appear in the later supplements, providing a framework for stringing your scenarios together and a system for improving your characters.
In my opinion, both games are great and each plays sufficiently different that I am happy to play either. So, that leaves me wondering which I should recommend. Well, that depends upon what style of play you want. Both systems work well but in different ways and both really have a different ethos behind them.
CiC offers a single package that gives you four warbands, six generic scenarios and a campaign system. It is focused on 1920s Cairo so you need to be interested in that if you want to play the game as written. If you want to play using this system but with different character types or warbands, then you will have to put a bit of work into your games.
45A offers a broader framework with more character types and greater freedom for creating your group. It does offer most of the pulp archetypes so you could play gangsters or archaeologists, but there are no supernatural elements in the core rulebook. 45A also focuses more on tailor-made scenarios and it encourages this style of creative approach. I have always felt that 45A wants you to put time and effort into making your terrain before the game and rewards a more creative approach.
When coming down to choosing between the two, I am hard-pressed to specify a preference. Both rules sets offer fun games with a different flavour. Each is simple to get into because of the low number of figures required. Really it will come down to what sort of game you want to play. CiC is slightly more generic in approach, like a more typical skirmish wargame, while 45A feels more like a light RPG in scope. Personally, I shall continue to play both for the different experience that each provides. If you prefer a single rules set with a generic approach then I think CiC will suit you better. If you want ot put a little more effort into your games and adopt the light RPG approach then 45A should suit you better. Or maybe, like me, you should just get and play both. After all, you can use the same figures with each.