I am assuming that you want to access the ebooks via the network rather than over a USB cable? On that basis with both the Calibre Content server and Calibre2Opds it will depend on whether the reader you select has support for the OPDS standard for online catalogs.
The main reason one chooses Calibre2Opds over Calibre Content Server is that it can be used in scenarios where you cannot (or do not want to) run the Calibre Content server) but can have a web site.
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