No, the 23 is the compact (same size as the 19), whereas the 30 is the subcompact (same size as the 26). Besides, the 23 is .40 and the 30 is .45 ACP. So different size and caliber.
Here's a good link to see and compare the different models/sizes of Glocks, since their numbering system makes no sense unless you care about when a gun came out chronologically.
http://www.glock.com/english/pistols_models.htm