I remember many years ago when they buffed the Space Marines (+1 toughness or something?) and said that originally they seemed super tough but had been less impressive last few years. My friends who played said the reason the Space Marines had declined was that they were the only faction that had a load of tanks and vehicles. Once they got round to inventing that stuff for everyone else, it levelled the playing field.
Those early Rogue Trader army lists and add ons were so weirdly all over the place. From the start, technically anyone could use anything, and you could basically just design your own vehicles.
Marines/Imperial Guard then got motorbikes, land raiders, jetbikes, landspeeders, dreadnoughts and grav attack vehicles while everyone else (which was basically orks and eldar at that point) got to use maybe a couple of stolen imperial bits. Orks had battle buggies, but they were shit.
Then imperials got predators and rhinos as well, everyone else (still just orks and eldar) got their own dreadnoughts, and everyone got robots, although Imperial were the only ones with any specific models, the others had to design your own.
The eldar got their own jet bikes and their own rules
Then the orks got Battlewagons, gobsmashas, and various weird custom vehicle options.
The marines/imperial guard had been designed early on and played from a fairly standard ruleset, as it were, whereas the later developed armies like orks and eldar had lots of weird special rules and weapons that kind of bent round the earlier ones.
Anyway, IMHO nothing beats an Imperial Guard assault squad armed with jump packs and vortex grenades. Except maybe an orbital bombardment of vortex missiles. Which you could do in the original rules.
