Wow, I finally tried out Cloud Readers and I really don't understand the hype. Quite underwhelming barebones app in my opinion. Hey it's free so I won't complain too much, but I won't be using it for anything. It skipped over the first few pages of the .cbr file I tried it with, and the sideways scrolling thing it does is just annoying. Features? UI? Severely lacking. I prefer Goodreader by a mile.
Soulcrux, CBRs and CBZs are just folders of images, RARed or ZIPped, respectively. The advantage is that it is compressed and one file instead of a folder, and that's about it. Personally I use a free app called Jomic to batch convert CBR and CBZ files to PDFs, which works splendidly. PDFs are more compatible and the same file size, in my opinion there is no downside. You have a lot more options for PDF readers than those other formats. Goodreader is only 99 cents and is has lots of great features and is working perfectly for me as a PDF comic reader. You can zoom in to exactly fill the screen and it retains the zoom level as you change pages. Some people seem to think it's slow but I have not had that problem at all.
How fast is Jomic?
The reason I ask is because I downloaded 30 Volumes of Batman arcs, and i was thinking that'd probably take a while to convert to PDF..