The spelling of the relatively simple word for 'more' in Greek, is in actual fact quite complex. The neuter single of the word occurs in three different forms in the Nestle-Aland editions (and I expect in two different forms in the Byzantine texts): πλειον, πλεον, and πλειω (the latter only in Mt 26:53 in the Nestle editions). It is no surprise then that there is some variation between these forms. Πλειον is the most common form, which has retained its diphthong before an /o/ sound. According to BDF §30.2, the πλεον form without the iota is the more literary one. It is remarkable how in Lk 3:13 the Greek tradition has almost universally πλεον. Some minor orthographic details manage to survive almost unharmed.
The πλειω in Mt 26:53 is problematic though. Πλειω is an acceptable way to write the neuter comparative of 'more', but its attestation is rather limited: Sinaiticus, Vaticanus, and Bezae. Bezae has in Luke frequently πλεον where others have πλειον, and also has the form πλειω in Mt 20:10, and Lk 21:3 (here with considerable additional support). I am not sure at all what to make of Sinaiticus, and Vaticanus in Mt 26:53. Though these two majuscules at times preserve a good, old orthography, here they are possibly a bit idiosyncratic and over-literary (as happens on occasion). Unless someone can convince me otherwise, I am hesitant to admit πλειω here.