My talking about the SF RPG of choice for my short campaign refresh and the subsequent reader comments got me to thinking about a design element that affects system choice: generic systems vs. systems which contain an implied setting. Secondary to this is the notion that a given system will also contain some tone and flavor; flavor might reflect the implied setting, but it doesn't need to.
For example: White Star has a setting that it has provided some support for, but the book itself is fairly setting neutral; it's got lots of content that might at times even seem contradictory (you have mecha jocks, space squirrels, star knights and embittered old preachers on the space frontier all in the same game system, for example). White Star's implied setting is schizophrenic; it's really a kitchen-sink universe if run exactly as presented, but the intent is to instead give you tools to make your preferred brand of cinematic-inspired scifi.
Contrast this with Stars Without Number, which on the surface seems to be a toolkit game. However, the foundation of SWN is written around a specific universe which has a defining moment called The Scream within it. All of the implied setting content (and SWN Is loaded to the gills with it) has this core conceit baked into the premise. If you run SWN with a different concept in mind it either limits the content of the book to your own vision or requires you to modify or ignore large chunks of the story content. By contrast, with SWN if you don't want Star Knights in your universe you just tell players they are off the table; the rest of the system won't break if you exclude them, and indeed some story bits might even feel more consistent as a result....that's because White Star isn't building you a toolkit for an implied universe like SWN is; it's providing you a toolkit for a flavor of gaming (cinematic scifi).
Contrast this with actual generic systems such as Cypher System, Savage Worlds, GURPS and even FATE. These systems might come with some inherent tone/flavor due to the underlying game systems, but each tries to support a wide range of settings without any implied content. GURPS can run both cinematic scifi and (if you were so inclined) the SWN universe in which The Scream happened. Savage Worlds is aimed at it's motto of Fast! Furious! Fun! but it more than amply tries to cover every SF genre it can within its own toolkit within the 3F parameters. Cypher System's underlying flavor is one of deceptively simple mechanics that are player facing with resource management baked in, but the Stars are Fire sourcebook spends half the tome giving you a vast array of ideas for any conceivable SF idea you can think of; it's selling system with a certain tone and flavor and the only implied setting are those which most benefit from the contrivances of Cypher's mechanical design.
The downside, as any gamer with full time work and family knows, is that generic systems often take a lot of time to prep. The seductive point of a game system with an implied setting like SWN or Traveller is that it does some of the work for you; if for example I simply didn't have a campaign vision in mind (and this is where I always trip myself up as I like designing my own settings rather than using existing content), then SWN would actually work really well for me, as I love its world/adventure chart design process. Likewise, Traveller is insanely processual in charting out its own implied setting through the rules, and you can run any universe you want with it so long as it involves dudes who muster out and start life as middle aged adventurers travelling using something like Jump Drive in a bizarrely flat hexagonal galaxy.
All of these systems are great, of course, and I've run all of them except for FATE (which I almost ran, but ultimately decided it's core mechanical conceits are just not my cup of tea). So when I am looking for what I need at the moment I am thinking of what my goal is....and it sort of follows this thought:
1. I want a system which can give me a 5-10 session arc that feels fulfilling but doesn't feel like we have to be obligated to keep playing (so, progression within 5-10 sessions is meaningful); any of the systems we're talking about could theoretically do this well, but I'll rule out GURPS because the setup will take too long for 5-10 sessions and Traveller because its progression is flighty at best.
2. It needs to fit my vision of a "realistic" space opera idea I have in mind with specific conceits for how stuff like hyperdrives and human expansion into the galaxy happened (and lots of aliens); this means it needs to be a good toolkit game with lots of premade stuff that fits the setting; that eliminates GURPS and Traveller (would have to build it all), SWN (implied setting would have to be redacted), and leaves Savage Worlds, Cypher System and White Star (all three have enough content, bt of course SW requires some conversion work).
3. It needs to be easy to run without a lot of rules adjudication, because part of the "palette cleanser" is I want a break from a system with a rigorous three-action mechanic and a 600 page rulebook. Yes, PF2 is remarkably easier to run than PF1 but it's still not "Swords & WIzardry" easy, you know what I mean? This conceit is the most important part!
With those three criteria in mind I could readily narrow the list down to White Star, Savage Worlds and Cypher System. As I identified in yesterday's post Cypher System would be ideal but the Roll20 randomizer for dice seems to actively hate my players so in the interest of sanity I decided not to go with it. Savage Worlds requires some (admittedly minor) conversion to work properly right now so I want least amount of effort....so White Star it is.
There is one element undiscussed: The explicit setting systems. Eclipse Phase, Star Wars RPGs, Star Trek Adventures....these are all games you play specifically for the detailed setting. They are in their own ballpark, as you will never likely want to use them for something that isn't a total riff on the actual universe the system supports.