Kindle vs iPad

I bought an Amazon Kindle last week.  So far I like this device very much.  I use both apple iPad and Kindle to read books, however, the biggest difference between these two devices is its weight.  iPad is, at least for me, too heavy to keep holding during long read.  On the other hand, kindle is light enough to hold for long time.  Indeed, I like Kindle's electric ink.  It is much easier to read than iPad display, especially in the outside.