I've been using the Kindle Fire HD 7" 32 Gb and Paperwhite to read the same eBooks the last couple of days. They each have their own advantages and disadvantages.
In bright light conditions the Paperwhite wins out totally. There is no glare while the Fire HD has lots of glare and mirror images. The brightness on the HD can be turned up to eliminate glare from the page but the side borders still reflect images and the light source.
Paperwhite at level 22 light of 24 in bright light has absolutely no glare.
I read reviews of screen glare protectors on the Amazon site and there are bad reviews (one star) on all with many defects: pixellation, leaving glue residue, bubbles, dust collection, etc. Thus, I'm using the Fire HD without a glare protector. The Fire 1st Gen did have one good brand glare shield but the manufacturer of that brand warned on the site it had a pixelation effect when used on the HD. That turned me off.
A notable difference in the reading apps is that the Fire HD shows page numbers and the Paperwhite does not. However, time left for chapter and book is shown on the Paperwhite but not on the Fire HD.
Collections are available on the Paperwhite but not on the Fire HD.
The big advantage of the Fire HD is the running of android apps like the GSam Battery Monitor and the Tecarta and Logos Bibles. The AcroBible was the best on the Fire 1st Gen but does not run at all on the Fire HD. Other apps I use on the Fire HD were the AccuWeather and Weather Channel apps. The first shows measurments of rain and snow and the second shows probability of rain and snow.
The Fire HD also runs my Netflix movies, my songs (great speakers) and can run free Amazon movies (Prime required). However, the Fire HD standard cover does not provide a stand like the Fire 1st Gen Marware cover did. Thus, the following stand is really a necessity:
I have Parental Controls on both enabled just to prevent accidental eBook purchases. On the Fire 1st Gen doing so blocked internet access. On the Fire HD it can block the purchases and leave internet access enabled.
The Fire HD even without Special Offers shows recommended eBooks at the bottom of the screen in portrait mode. They can be turned off in the Settings and then turned on again if one needs a new eBook.
For just reading eBooks, the Paperwhite is way ahead of the Fire HD.
The Fire HD 7" 32 Gb started out 26.68 Gb for 26.96 Gb space available. After installing all my "stuff," 24.43 Gb was left.
2.25 Gb was used: Books = 57.30 Mb; Audiobooks = 15.30 Mb; Music = 1.28 Gb; Video = 120.00 Kb; Photos = 47.75 Mb; Docs = 12.12 Mb; Apps & Games = 350.14 Mb; Others = 743.65 Mb plus other system supplemental use.
So far I really have no uses for all that extra memory. However, I can see its use in the future for apps not yet developed. It doesn't hurt to have exta capacity as new innovations come to market since no additions can be made to memory after purchase.
Comparative weights of the Kindles WITH standard covers:
Kindle Fire HD 7" 32 Gb = 1 pound, 2.9 ounces
Kindle Paperwhite = 11.9 ounces
Kindle Fire 1st Gen = 1 pound, 4.2 ounces
Kindle Kbd WiFi 3rd Gen = 13.6 ounces
With WiFi time enabled all the time on the Fire HD 32 Gb and Paperwhite one can switch between them fast without pressing any sync keys. The GSam Battery Monitor indicated decisively that WiFi uses very little power compared to screen power requirments. I use the Paperwhite near a window with bright light and the Fire HD at night in my computer room at a desk which does not reflect glare due to its placement.
One big plus for the Fire HD 32 Gb is the ability to run Amazon Prime Videos (free) and they run great - much better than videos ran on the Fire 1st Gen. Sound is superb and HD rendition is great. The Paperwhite cannot do that. Plus, the videos are saved to the Carousel and bookmarked to be watched in segments.