i've got a 7" Amazon Kindle Fire and use it primarily as a comic reader. i use the "Perfect Viewer" app to read .cbr comic files.
i find the size is good for me, but, depending on the comic, the font can be quite small sometimes. for double-page spreads, i always have to view it landscape style and then zoom in to get the full effect. also, anything scanned thru fiche will be harder to read because of the lack of quality. Just some things to keep in mind.
i hope you enjoy whatever you end up with tho!