While i don't have a kobo aura one , all kobos have the same firmware, i got a kobo aura 2nd edition so i know the ecosystem. I also own a Oasis 2.
4)
To answer your question about turning pages in horizontal mode on the kindle Oasis 2, I prefer to turn pages by tapping rather than clicking on the button since it is in an awkward location, I have to say i have small hands. In the kobo ecosystem you can't read in landscape mode unless you have Koreader installed(jailbroken firmware). The buttons are very useful to me on both my Voyage and Oasis, i usually read in vertical mode.
5)
Concerning the speed of page turning on the oasis 2 , it slightly faster than my Voyage and Kobo Aura 2nd edition, as far as i know it is the fastest E-reader out there since it uses a newer processor.
6)
To read PDFs on an E-reader you need an app on jailbroken firmware, unfortunately you can't jailbreak the oasis 2 , but kobos are easy to jailbreak, Koreader reads pdfs/epubs/cbr/zip very well,it has highlighting support and dictionnary support and many more features, if you want to read pdfs on your E-reader Koreader will be very useful.
(
Koreader Wiki)
7)
I find it hard to hold my Oasis in one hand without any support since it has a larger screen and i got smaller hands though I have to say it is comfortable, I like the fact that I can turn pages with either my right or left hand since the screen can rotate. In kindles, you can modify the boldness,the size of the font,you can even add your own fonts , you can do that on the kobos as well.
One feature I like in the kobos is tracking your reading statistics. Telling you how many books have you read, how much time have you spent on reading them.(
reading stats).
But the reason I would pick a kindle over a kobo for now is the fact that there is no software to manage your notes and highlights on kobo. Kindle mate(
http://kmate.me/), helps me check my notes, track the words i have looked up in the dictionnary.Import my notes to my computer.
Concerning the screen quality 300 ppi is perfect, it is the quality most books are printed in. It is comfortable. The frontlight on my KO2 is great.
Finally if you are buying the E-reader both to read on the go and at home, go for a smaller screen, the kobo aura one is too large 7.8", the downside of the Kindle Oasis 2 compared to the paperwhite(6") is the fact you can't put the KO2 7" in your pocket.
I am sure if you buy the KO2 you will find the battery life is smaller since it has a 1,000 mAh(paperwhite 1 1,470 mAh, Kindle Voyage 1,320 mAh) , mine lose 2% per day with no use, but it is ok for me since i can read up to 600 pages before it reaches 40%.
The Kobo Aura one has 1,200 mAh with a larger screen 7.8".
You will find a small comparison between E-readers here.
I do hope you this has helped you