I have some versions of Stars Without Number - free downloads, so I'm not sure where they're at relative to the state of the art of that system.
I currently have an active Classic Traveler game, so I was curious (i) which adventure have you converted, and (ii) what SWN offers that's different from Traveler?
I converted Pirates of Drinax Module 1 - Honor Among Thieves.
I may or may not use the rest of the series, it was mainly something to jump start the game. My idea is to set the campaign in motion, open the game up to a sandbox style, but sprinkle in other modules from the series here and there.
I've played a bit of Classic Traveler back in the day (but I haven't touched it in quite a while, so my rules knowledge is hazy).
From my point of view, it provides a similar game experience. It sits in that more hard-scifi than Star Wars/Star Trek style game and supports a sandbox approach. SWN does this by providing a 'tag' system to planets and systems. Tags are pre-packaged environments/situations that can be applied to a planet and provide a baseline 'what's going on with this place' that can be expanded upon when needed. They're kind of a short hand for noting what kind of adventures can be had on a given planet.
You can create a couple systems with planets and give them a couple tags each and have enough to tell players what each system is like. Then if they decide to go to one, the tag gives you enough prompts to build out an adventure or even improvise if needed.
I'm using SWN because it uses classic D&D rules as its back-bone, so it is immediately familiar to anyone who plays 5E or B/X or any other D&D (which is the case for my group). I think SWN is, in general, less detailed than Traveler, but I can see importing some Traveler subsystems into SWN without much issue.
It is both a complete game and a toolkit. It provides a very loosely defined base setting but leaves a lot to be developed. It does not include any default alien races (or even require such to exist). The existence and nature of Alien cultures, A.I. robots droids, transhumanism, etc... are all up to the GM/players to determine It does provide very complete and detailed rules for each of these concepts, but the game leaves it to you to include or exclude them.
The game uses character classes instead of life paths. There are 4 classes... Warrior, Expert, Psychic, Adventurer. Warriors are your soldier types they have the best hit points and are good with weapons (they have a special ability to turn a missed attack into a hit or negate a hit against them once per combat). Experts are skilled characters (they have a special ability to re-roll a failed skill check once per scene). Psychics possess psychic powers. Adventurers represent a cross-class or multi-class character. My game was 1 Warrior, 1 Adventurer (Warrior/Expert), and 4 Experts. The 4 Experts felt unique and each contributed to the game (there was a little overlap in skills, but they weren't carbon copies). To me, even though it is a class system, it maintains a lot of differentiation and supports unique character concepts.
The system is pretty straightforward. Skills work like Traveler skills - you can have a skill at 0 to 4 or 5 I think. 2d6 + skill + ability mod vs a target number. I'm not 100% sure how this compares to Traveler, but it assumes an 8 is a challenge for a professional, 10 is world class challenge, 12 represents something extremely difficult to someone who is top in the field. There are elements called Foci that work like feats - they grant special knacks and tricks that specialize your character. You can have two characters with Program-1 but the one with the Hacker Focus will be more specialized.
Attacks are d20 + skill + ability mod vs AC. We only had one combat so still learning the game, but for the most part it plays like old school D&D. At low levels combat can be very deadly. You do get additional hit points as you level. Psionics exist, but none of my players rolled up a psychic so I haven't seen those rules in action, yet.
We didn't get into starship combat, it does seem like the ship combat subsystem may provide opportunities for characters not built for space combat to contribute. There are rules for time it takes to travel intra-system and time it takes to jump to other systems. This is important because there is a cost per crew per day in operating that needs to be accounted for. The scale of the game is interesting for someone who usually runs fantasy. It can take a couple days to get from the edge of a system (where you arrive after a jump) to a planet... I'm used to players hiking a few hours to the dungeon.
