Will Apple's iPad Bite Into Amazon's Kindle Sales?

(Apple iPad poll updated with debut weekend sales figures.)

NEW YORK (TheStreet) -- Since the launch of Apple's(AAPL) iPad on April 3, many comparisons have been made: "It's just a big iPhone," some have argued; others have wondered if the iPad is merely a prettier version of Amazon's(AMZN) Kindle e-reading device.

Regardless of what one makes of the iPad, the tablet is undeniably pretty, and boasts a more exciting interface than that of the Kindle. Meanwhile, Amazon has been bickering with large book publishers over e-book pricing models, and appears to have conceded to the battle to a significant degree.

More than 300,000 iPads were sold on April 3, according to Apple. That exceeds the estimates of some Wall Street analysts, who were predicting sales of 250,000 to 350,000 units over the weekend, according to Reuters. Furthermore, Apple said that more than one million applications from its app store and more than 250,000 e-books were downloaded by users.

In advance of the iPad's launch, Amazon in late March unveiled screen grabs of its free Kindle apps for tablet computers, including the iPad. Amazon stated that with the apps, readers would be able to access more than 450,000 Kindle books on their tablet computers, including the iPad.

Amazon is currently offering New York Times best sellers and new releases from $9.99.

Amazon said that Kindle for tablet computers will include Whispersync technology, which automatically syncs the user's last page read, bookmarks, notes and highlights across Kindle and Kindle compatible devices. "Customers can start reading on one device and, on another, pick up where they left off," Amazon said.

Meanwhile, the fact that Apple's iBookstore can be accessed only after the free iBooks application is downloaded onto the iPad increases the likelihood that users could end up downloading the new, free Kindle apps instead and buying e-books from the Kindle store.

Of course, how Kindle's e-book sales could be affected if Apple is able to pre-install the iBooks application on future iPads remains an open question. The starting price for iBookstore books will reportedly be similar to that of Kindle's.