I would definitely go with an Android Tablet of some sort.
There are several nice ereader Apps available already for Android, with more coming all the time.
FBReader is available for Android, and it does handle CHM format, but the results can be hit or miss because some CHM authors use hacks specific to Microsoft's implementation.
But Android devices have more sophisticated HTML browsers than typical EPUB and other readers, and since CHM is internally HTML based, an Android tablet would probably be your best bet of finding a solid CHM reader.
As far as which one goes . . .
These tablets are rapidly becoming commodity items like PCs and Netbooks, so just shop around and check out several review sites.
The relevant questions are very similar to a PC or Netbook -
- What is the screens physical size and resolution?
- How well does the touch screen work and does it effect the overall sharpness or clarity of the screen?
- How much memory and how fast is the CPU? (Look for review comments about multimedia performance, because MHz don't always translate)
- What version of Android is it running, and can that version be upgraded?
- Is it fairly easy to 'root' the device so YOU can control what Apps are loaded?
. . .and the all important -
- What is the REAL battery life in verious situations like:
- - when used in low CPU activity applications like reading?
- - when used in higher CPU activity applications like video playback?
The only reader on your list that I have seen is the PocketBook IQ 701 and I thought it was pretty nice little tablet for the money. You can find lots of comments as well as several fairly complete reviews both here and all over YouTube.
Here is a fairly well balanced review from the-ebook-reader.com that spicifically addresses using the IQ 701 tablet as an E-Reader -
http://www.the-ebook-reader.com/pocketbook-iq.html
Note that, as mentioned in the review, most of the minor glitches he mentioned have already been fixed in later updates.