Well, let's see...
CGen...
CT:
Stats 2d each
Rolls: Enlist, Survival, Commission (until commissioned), promotion (only if commissioned), Reenlist.
Skills: 1 per term, +1 for 1st term, +1 for commission, +1 for promotion; some services have an additional skill for certain ranks
4 skill tables: Pers Dev, Service, Adv Ed, Adv Ed 8+
Aging: starts at 34, make saves for each indicated att by rolling on 2d for N+ where N is from table by age and which stat.
MT:
Stats 2d each
Rolls: Enlist, Survival, Commission (until commissioned), promotion (only if commissioned), Special Duty, Reenlist
Skills: 1 per term, +1 for 1st term, +1 for commission, +1 for promotion, +1 for Special Duty, +1 if Commission made by 4+, +1 if Promotion made by 4+, +1 if Special Duty made by 4+; some services have an additional skill for certain ranks
4 skill tables: Pers Dev, Service, Adv Ed, Adv Ed 8+
Same as CT
TNE
Stats: 2d-1 each
Rolls: Enlist, Survival, Commission (until commissioned), promotion (only if commissioned), Special Duty, Reenlist
Skills: 1-4 for terms after first in career, +1 for commission, +1 for promotion, +1 for Special Duty, 1st term up to 7 levels base
Skill tables: pick skills from list for career
Aging: saves when indicated on table. Save rolled by rolling stat or more on 1d16-1
T4
Stats 2d6
Rolls: Enlist, Survival, Commission (until commissioned), promotion Special Duty, Reenlist
Skills: 4 per term, +1 for 1st term, +1 for commission, +1 for promotion, +1 for Special Duty; some services have an additional skill for certain ranks
6 skill tables: Pers Dev, Service, Ed, Adv Ed 8+ (don't remember titles of other two)
Aging: don't recall.
MGT
Stats 2d6 each
Rolls: Enlist, Survival, Commission or promotion (but not both) (Also serves as reenlistment). An event is also generated. Note that each career has 3 sub careers.
Skills: 1 per term, +1 for 1st term, +1 for commission, +1 for promotion; all services have an additional skill for certain ranks. Many events grant 1 level of skill, a few grant 2, some grant none. Some rare events grant
6 skill tables: Pers Dev, Service, Adv Ed 8+, plus one per each sub career.
Aging: roll 1 save per term starting at age 34, on 2d-terms, 1+ saves; 0 or lower costs 1+ points (up to 6P 2M)
CT/MT advanced:
Roll yearly for posting, and that determines yearly survival, promotion,decoration and skill gain checks.
TNE/T4: no advanced
MGT Advanced: additional careers springboarding off of base careers, otherwise no different from basic.
Personal Combat
CT: damage to stats, armor makes to hit harder
MT: Hits≅1/3 total of STR+DEX+END; Damage to hits, Pen:armor ratio reduces damage, margin of to hit increases. Post combat, hits damage becomes CT-style damage to atts.
TNE: Damage to location HP derived from Con & Str. Pen:armor affects damage by reducing dice.
T4: Damage to stats; Armor stops dice of damage.
MGT: Damage to Stats; Armor stops points of damage, margin to hit increases damage.
Task System:
CT: none explicit; Combat uses 8+ to hit; non combat includes some multi-die for stat or less, some 2d+skill for X+, and some other variations.
MT: 2d+A+B for N+, N by difficulty level for success, 3d-A-B for time. A and B may be Stat/5 or skill level.
TNE: 1d20 for (Stat+Skill)x L; L is difficulty level modifier (x4 to x1/4).
T4: Xd6 for Stat+Skill or less X is difficulty level based.
Ship Design:
CT Bk2:
letter drives,
2 axis (price, displacement).
PLas, BLas, Msl, Sand; all turrets only
No screens, no armor
CT Bk5:
% based drives,
3 axis (Price, Displacement, Power).
Turrets- BLas, PLas, Msl, Sand, Plasma, Fusion, PA
Barbettes- PA
50T Bays- Plasma, Fusion, Missile, Repulsor, Meson, PA
100T Bays- Missile, Repulsor, Meson, PA
Spinals - PA, Meson
Screens - Meson Screen, Nuke Damper, Bl. Globe
MT
4 axis: Power, Volume, Mass, Price
% based drives, 3 axis (Price, Displacement, Power).
Jump fuel 5xJDriveTons, not 10Jn%
Turrets- BLas, PLas, Msl, Sand, Plasma, Fusion, PA, Disintegrator
50T Bays- Missile, Particle Accelerator, Plasma Gun, Fusion Gun, Repulsor, Meson Gun, Disintegrator, Tractors, Jump Damper
100T Bays- Particle Accelerator, Missile, Repulsor, Meson Gun, Tractors, Disintegrator, Jump Damper
Spinals - PA, Meson, Disintegrator, Jump Projector
Screens - Meson Screen, Nuke Damper, Bl. Globe, Wh. Globe, Proton Screen
TNE
5 axis - Power, Volume, Mass, Price, Surface Area
Weapons: BLas, PLas, Msl, Sand, PA, Meson, Plasma, Fusion. Build them all to any size mount.
Screens: Meson, Nuke Damper, Bl. Globe, Wh. Globe
MGT
2 axis - Price, Volume
Under 2000Td, Letter drives; Over 2000Td, % drives
Turrets: Msl, BLas, PLas, Sand, PA, Meson
Barbettes, 50T & 100T bays: Msl, BLas, PLas, Sand, PA, Meson, Ortillery
Generally: CT, MT, and MGT are all sufficiently compatible that characters can be used with only minor changes.
The MT task system can be backported seamlessly. The MGT task system can be as well. CT and MGT have similar damage mechanics
MT ship designs can be used with CT-HG (& vice versa), but the design rules are very different
MT combat can be swapped out with CT combat with no real difficulty, but they can't be combined well.
MT Cgen is very similar to CT, but adds SplDuty, and increases the number of cascades (and thus player choicees) dramatically; about 1 extra skill per term on average is gained; use of either is pretty much the familiar for the other. Drop the Sp Duty rolls and bonuses for high Comm & Promo, and it produces characters with the same levels as CT basic, but access to the full range of skills from adv. gen.
MGT CGen is very different, but produces characters with similar total skill levels to MT. The skill list is also quite different.
TNE is really an incompatible game; it was a force-fit of the setting to the T2K/DC rules.
T4 is again, character incompatible, due to very different assumptions about skill gain rates (more than TNE!), but the CGen tables could be used for CT/MT by using the CT or MT skill gain rates. Combat mechanics can be back-ported without problem to CT/MT, or front-ported to MGT; just convert the tasks to their MT or MGT equivalent difficulties.
MGT and CT Bk2 designs are similar approaches
CT Bk5 and T20 are functionally the same (except for Airframes and Computers; It's often smaller in T20.) CT Bk5, T20, and MT all use the same system of UCP ratings, so porting stuff from one to the other is actually pretty straightforward, Except for MT Fuel Rates.
