Apparently the alexandrian manuscripts were different from the other manuscripts but thats a scholarly dispute I havent actually seen them myself so dont quote me Im not an expert!
They may have been older physically but the ones that were used were copied many times and handed down and thats why the older ones were preserved more cos they werent used. The reason why they werent used, and scholarship bears this out, was cos scriptures were omitted ie. they werent usable copies.
Were verses omitted in the Alexandrian manuscripts (e.g. the oft-maligned NIV) or does the received text (e.g. the KJV) contain verses added?
A common principle in textual criticism (which, admittedly,
does have its detractors) is to prefer the more difficult reading when confronted with multiple manuscript variants. The idea is that later scribes were known to add explanatory glosses and interpolations; compare to the many targum paraphrases and rabbinic commentaries. Read some of Robert Alter's translations of the Hebrew Bible, and you'll find his commentary often addresses glosses by scribes amending the text.
A minor example (in all bibles) is found in pagan theophory, that is having the name of a pagan god as part of one's name*. According to 1 Chronicles 8:33, King Saul's son is Eshba'al whereas in Samuel,
Ba'al is replaced with
bosheth, or shame; thus Eshba'al becomes Ish-Bosheth. A similar phenomenon may be seen in Jerubaal (otherwise known as Gideon) and the god Ba'al-zebub and Beelzebul and
possibly Jezebel.
SO, the accusations levelled against the Alexandrian manuscripts as they variously minimise the blood or deity of Jesus may indeed be used to question the authenticity of the received text.
* Michael, Gabriel, and Elijah are other examples of theophory.
This has nothing to do with Egypt, sorry...