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There is no difference between the first and last printing other that errata fixes, if any.
As long as the exam number doesn't change there should be no major changes, other then the one previously mentioned.
You can always verify this at "Cisco Press" when in doubt. Since they handle all the official Cisco certification products. You can confirm this information directly at Cisco Press at the following links:
Also if any change will be issued on the CCNA Wireless Certification exam or content, you will see a notification ahead of time at the following link:
If needed you can confirm the Exam Topics here:
I hope this information is helpful for you.
I would not worry about the two printings, they are usually the same content, like you said, may contain errata corrections.
Keep an eye on the printers website, for errata notifications.
You can find errata notifications under the "updates" tab on this page:
Good luck with your studies.