This hypothetical battle of Roronoa Zoro of One Piece against Sasuke Uchiha of Naruto has been a subject of very hot debate. It is a duel between two great swordsmen from different fictional worlds, each with different special powers and abilities.
In this comparison, these characters are at completely different times of development. The argument is usually that Sasuke, in his prime, with peak physical potential, would hold greater power than Zoro in that he remains in a developmental phase and is nowhere near his maximum potential. This tends to suppose that if the fight were taken to be current from their perspective series, then Sasuke may have the upper hand because his powers are more fleshed out.
Others point out that Zoro does gain too much of an advantage through physical strength and ability wielding a sword. In support of this is that most of the time, his strikes are equivalent in power to high level Jutsu within the Naruto verse, meaning only something as strong as Kirin would be capable of matching Zoro's raw power. This focuses on the fact that Zoro has better physical stats than Naruto, and that his techniques with the sword are much more powerful in terms of destruction.
The fight dynamic between Zoro and Sasuke would probably be based on swordsman skills. In hypothetical situations, the two are often perceptively paired in close-range combat, which places them in a dilemma as they engage each other with their swords in trying to outstep each other. Sasuke would have problems with Zoro's unique three-sword style, as it would probably present an advantage in close-combat situations.
Another speed factor of the match is the swiftness of the two combatants. A few analyze that current Zoro is actually faster than some versions of Sasuke, particularly those who could not access his most premium abilities. This speed edge can be very, very crucial in a fight of two sword masters who have gained their names and reputations based on the split-second maneuvering on their crafts.
There is the fact that Sasuke can do various things, particularly on account of his Sharingan and the techniques it can use. The possibility of Sasuke using genjutsu thereby creates the argument that this would alter much, but it is usually mentioned that Sasuke is not a heavy user of genjutsu in most of his fights, therefore diminishing this potential advantage).
This may also depend on how certain techniques are effective on each other. For example, nobody here can really say much about how Sasuke's Amaterasu would work against Zoro's swords. Some believe that if Amaterasu were to stick to Zoro's swords, it would render him unworkable and seriously handicap him. This scenario alone would lead one to consider just how each unique capability of characters might be able to interact against one another.
This hypothetical result could go either way, depending on the versions of the respective characters being pitted against each other. For example, a battle between the base Sasuke (without Mangekyou Sharingan or Rinnegan) and Zoro is most definitely not the equivalent to a battle with Sasuke at his fullest potential. These slight differences play their very important role in every discussion or debate which comes up in fans about what such an actual fight could yield.
Some of the hypothetical situations the fans come up with include the fact that Zoro and Sasuke are going to have a very heated, breakneck-speed battle. Imaginary battles include a rush of exchanged sword techniques at the very peak of the practitioners' abilities. In all the scenarios, this pairing harbors great appeal to the fans through the noted skills and determination of both characters.
Other discussions suggest leveling some aspects of characters to make a fair comparison, such as speed, or they pinpoint specific versions of both characters. So, in the end, the idea is to be much fairer and more entertaining in the hypothetical battle, to make it as truthful as possible to each main ability or character it is seeking truth in and not to the power scaling of a universe over the other.