okay let's weight up both blood line limits then shall we?
Sharingan is the blood inheritance limit of the Uchiha Clan. The Uchiha are said to be descendants of the Hyuuga, with the Byakugan changing into the Sharingan over time. This doujutsu (eye skill) gives one the ability to read Genjutsu, Taijutsu and Ninjutsu and then defeat it. As such, the clan member can view a technique being performed and almost instantly memorize the movements required to be able to complete it, including the needed chakra moldings and seals used. However the clan member cannot copy techniques that are unique to another bloodline and the clan member must have a body capable of meeting the chakra and physical requirements to do the jutsu. This rarely stops the clan member though, as such stressful situations often push their limits farther and allow them to harness their full potential.
The Sharingan itself contains three tomoe (comma). A higher mastery of the Sharingan can be seen in the creation of a new tomoe in the eye, with three tomoe being the typical highest form of the eye. The rare Mangekyou form is a unique evolution of the Sharingan beyond the three tomoe form. An eye possessing two tomoe can allow the Uchiha clan member to track the movement of an opponent and do some minor copying of an opponents attack. For avoiding incoming attacks, the Uchiha's speed and agility will greatly control whether they can move to avoid it. However, three tomoe will greatly help in this area. It can also allow the ninja to pierce Genjutsu and see the surrounding reality for what it really is. It can also allow the member to pierce another’s body and see their chakra. While the eye is not refined enough to see the tenketsu and chakra circulatory system like the Byakugan, it can view the movement and flow of chakra. This can help them tell if a person is trapped in a Genjutsu, or if an attacker is a real threat or merely a bunshin.
An eye containing three tomoe will allow the ninja to see the image of an attacker’s next move from the slightest muscle tension in their body. This prevents wasteful movement and allows the Uchiha clan member to conserve much needed chakra in battle. It allows them to synchronize their movement to strike at an area moments before their opponent is even in that spot, essentially allowing them to strike out and hit their opponent before they're even there.
Three tomoe also grants the Uchiha the ability to do Genjutsu and hypnosis after locking eyes with an enemy. This can be used to cause their opponent to do an attack of the Uchiha's choosing. This hypnosis can also be used as a Genjutsu counter, which is the ability to turn a Genjutsu spell back upon the original caster without the requirement of forming any handseals.
i'll have more on the byakugan later. i'll give my opinion later