Personl Documents syncing works just like it does with book bought from the Kindle Store.
(Actually, with the exception that you can choose either old MOBI, or AZW3 without covers in Cover view. Plus that pesky Personal label obscuring the bottom quarter-inch of the cover.
)
Also, neither the Kindle nor the Kobo will show you real page numbers. But the Kindle will not lie to you about it, whereas most RMSDK-based readers will lie and make up pseudo-random
guessed numbers.
I say go for the Kindle -- there is nothing to compare with Amazon's synced Peersonal Documents!
(P.S. Don't apologize for using this forum for its intended purpose.
)
(P.P.S. Your English is better than
some many native English speakers'.
)