I would say they are as good as their users. Depending on the users, the Byakugan could be stronger or weaker.
The thing is, we have 4 main characters of the Uchiha clan (Madara, Obito, Itachi, and Sasuke) with tons of time on their hands. On the other hand, however, we did not get any main character that represent the Hyuga clan. Perhaps that what caused this misconsiption so to speak.
Also, it's kinda unfair to compare them as they stand now. The 4 previously mentioned characters have tons of fights to show off the Sharingan's abilities, and there are other characters with the Sharingan as well who got a lot of battles (Kakashi for example, you could throw Danzo and Shin in to). Where the last actual battle that a Byakugan user had was basically Neji Vs Kidemaro (or whatever his name was, the spider one) in part 1.
Yes, Kaguya is the strongest character, but it just show that the eye is as strong as its wider. It does not make sense to compare Madara to irrelevant hyuga member either.
The only way this comparesion would make sense is if we have characters that are exactly at the same level (or around the same level), and then compare their abilities together.
Or at least, that's how I see it.