Troops recruited at colonies are in general identical to troops recruited at the homeworld, given that several conditions are true:
Firstly, the type of troop must be the same. I expect this is obvious, but if you're recruiting advanced infantry from the Military Academy you built on your homeworld, it's going to be better than the standard infantry you're recruiting on your colonies.
Secondly, the species of the unit must be the same. The base attack and defense scores as well as the unit upkeep are dependent upon the species of the unit, not the founding species of the empire, and the species of the unit is dependent upon what the dominant species of the colony is at the time the unit was ordered into existence. If your homeworld is full of Atuuks, and you're recruiting regular infantry both there and at a predominantly-Naxxilian colony, the troops recruited at the Naxxilian colony are going to be a lot better than the troops recruited at the homeworld, because Naxxilian troops cost 40% less upkeep and have about twice the base attack and defense score that Atuuk troops have. Note that BattleBot units are identical regardless of the predominant species of the colony upon which they're built; Naxxilian-built BattleBots and Atuuk-built BattleBots are identical in every respect. You can find a listing of the base strengths for units of each species
here (the chart does not list BattleBots, but in terms of the numbers in that chart, the base strength score for a unit of BattleBots is 60). In-game attack/defense strengths are found by multiplying the values in that list by 100/100 for standard infantry units, 300/150 for armored units, 200/100 for special forces units, and 50/75 for planetary defense units; I don't remember off the top of my head what the bonus to the elite infantry from the Military Academy is, but it might be something like 150/150 instead of 100/100. Bonuses from technologies multiply the net value, so a fully-upgraded basic Teekan infantry unit has 65 (base value) * 100 attack * 1.5 (+50% attack strength from technologies) = 9750 attack strength and 65 * 100 * 1.75 = 11375 defense strength. Unit upkeep reductions are also species-specific rather than being dependent upon the founding species of the empire, and the upkeep modifier from the species of the unit stacks multiplicatively with troop upkeep modifiers from government type, leaders, and technology. Note that BattleBots are a bit special and count as standard infantry for the purposes of determining base strength but do not benefit from any of the bonuses to unit strength at time of recruitment.
Thirdly, the colony must not be host to the Fortress of Torak, which, if I recall correctly, applies a +100% bonus to the attack and defense scores of troops recruited at the colony (including clones but excluding BattleBots, if I'm not mistaken).
Fourthly, there are a handful of species which get bonuses to troop strength if the colony at which the unit is recruited has stockpiles of certain resources at the time the unit is ordered into existence, so if you're playing with some of those species and not all of your colonies have stockpiles of these resources, that can cause discrepancies in the initial strength of units recruited at different worlds. Bonus strength from resources is added to the base strength for the species, so the base score for Naxxilian units is 129 without Jakantra Ivory and 139 with it.
Fifthly, I'm not positive, but I think there might be a trait or two for Troop General characters which affects unit strength at time of recruitment. Not sure about that, though; I don't honestly pay too much attention to characters while playing the game.