I've enjoyed reading manga on all of my Sony devices (converted to .epub). I've even found reading on the 350 with its 5 inch screen very comfortable, due to the increased pixel density (the 350 can't take an SD card, though). I've never read manga on a Kindle, so I don't know how much the experiences differ. I usually load manga in .epub format onto an SD, and that way I can have several volumes with me at once. I find it very convenient.
The great thing about tablets, though, is the various manga apps that exist, so that you can read manga directly onto your device without the need to download and/or convert the manga onto your computer and then upload it to your ebook reader. I haven't rooted my T1, so I don't know how well Android manga apps work on it.
An ebook reader is the perfect size and weight (IMHO) to carry in your purse so that you can read manga on the subway (manga is my preferred subway reading). The Lenovo A1 is seems quite portable, but perhaps a bit heavy for one handed reading, if that's what you think that you will be doing with it. I do read manga on my iPad, using manga apps, but I find that I prefer reading manga on my T1 - I find the white background on the iPad to be too bright, even when I turn the screen brightness way down. Your best bet, I think, would be to try out some manga at a store on a tablet, to see if you are comfortable reading on a backlit screen. I don't mind reading on a backlit screen for short bursts of time, but I do prefer eink. You will probably find checking your email and doing light web browsing on any eink device a bit cumbersome; you would be better served by a tablet for that sort of thing. Personally, I like having both. If you really don't like the Kindle, you could sell it, buy a T1, and then get a cheap tablet as well. If you have any friends in the U.S. ask to see if any of them can pick up a T1 for you at Target - I've read here at MR that they are on sale for $60 at some Target stores.
Sorry for the long post that probably didn't help vey much
I do love my T1, for what it's worth, and would wholeheartedly recommend it to anyone looking for an eink device.