A couple things come to my mind in comparing the 2 devices.
One, the DR is not designed to be your primary portable computing device where the LE appears to be.
Two, the LE is a much larger and heavier device. Consider the numbers:
The DR-
* Height: 10.56 inches
* Width: 8.55 inches
* Dept: 0.472 inches
* Weight: 20.1 oz.
The LE-
Dimensions
11.65" x 9.64" x 0.74" – 0.87"
(296mm x 245mm x 18.7 – 22mm)
Weight
3.3 lbs. with Standard Battery
4.3 lbs. with Extended Battery
The DR is designed with 2 functions in mind, reading it's particular types of documents, most notably PDF's, and writing on documents for later importing to typed text. In my personal experience, it does both of those things pretty well even with the battery life issue.
I prefer the DR's e-ink screen to lcd for lots of reading, but that is a very personal preference and may not match your experiences or preferences at all.
For all that, I'm a big fan of tablets that work well. The LE is a very interesting looking device, and I would definitely have to dig in and do some serious research before I decide one way or the other.
LE1700 Review:
http://www.pcmag.com/article2/0,2817,2107214,00.asp