The Chris Pinto vs. James White debate on whether Codex Sinaiticus is a modern forgery can be boiled down to a few considerations.
1) Constantine Simonides claimed that he wrote the document based on collating pre-existing manuscripts, and that his uncle corrected the document.
Both sides agree that he so claimed. Dr. White demonstrated that these claims are essentially impossible, as explained below.
2) The most sympathetic source for Simonides says that Simonides was not a truthful person.
Dr. White raised this point, and Pinto did not dispute it except to say that this source was not the only supportive source and that the source himself says Simonides did not always lie.
3) There are no known examplars that could have been the source for Codex Sinaiticus.
Dr. White raised this point, Pinto's response was to point out that the source(s) could be as-yet-unknown manuscripts on Mt. Athos.
4) Codex Sinaiticus was written by several different, distinguishable scribes (as evidenced by different handwriting, different style of abbreviations, and different accuracy of work).
Dr. White raised this point, Pinto did not respond to it.
5) Codex Sinaiticus has corrections by multiple different correctors.
Dr. White raised this point, Pinto did not respond to it except to say that two other men (a monk and a scribe) may have been involved in the corrections.
6) The amount of time necessary for collating multiple manuscripts of the entire Bible (plus some apocrypha) would have been prohibitive in the timeline proposed by Simonides.
Dr. White raised this point, and Pinto responded that possibly his uncle started on the project years before Simonides began.
1. Regarding the Mt. Athos manuscripts, there is an on-going digitization project (link). At one point, Mr. Pinto alleges that the one way to resolve the mystery was to explore the Mt. Athos library for manuscripts corresponding to Simonides' claims. He won't be able to stand behind that argument from ignorance forever.
2. Simonides himself states that the collation began after Simonides himself joined the project, as demonstrated by Dr. White. So, although the uncle allegedly had corrected the other manuscripts in advance, the collation project had not been done in advance, according to the primary source for Mr. Pinto's theory.
The fact that the manuscript was written by several different scribes and was corrected by numerous additional hands makes it impossible for Simonides' story to be true. The necessary hypothesis would be that Simonides deliberately altered his handwriting several different times during the writing of the manuscript to give the impression of different scribes. Such a hypothesis is simply implausible - there is no reason for Simonides to do this for the purpose of creating a text for the Tsar (as he claimed).
The fact that collation of documents takes an enormous amount of time, especially when one of the documents is not in the base language (allegedly one of the manuscripts was a Syriac manuscript), also weighs against Simonides claim. While it might be conceivable that such a collation could take place, the necessary time and training for such a collation to be undertaken are simply not there.
The fact that the supposed exemplars of Sinaiticus do not produce the unique readings of Sinaiticus and the fact that some of these unique readings are found in later discovered papyri also weighs against Simonides' claim.
In view of these facts, it's hard to see how anyone could come to any other conclusion than that Simonides was not the scribe of Sinaiticus, whether or not Simonides actually did create a manuscript intended for the Tsar.