Download over SVN fast for small files, slow for big files

Question

A java file being much smaller than a jar (which is a big binary file, acting as a zip archive), the average speed will seem much faster, since the small file (a few KB) is downloaded in less time than svn polls the download speed.
That gives the impression of a high average speed.

But for a big file, svn has the time to poll multiple times that same download speed, and the actual speed is revealed (over a longer period of time).

Another aspect which can influence the speed transfer is the double-compression issue on https session:

when OpenSSL is built with zlib, it will automatically compress all data sent over an SSL connection. You can see this in the initial handshake "Client Hello" and "Server Hello" where client and server agree on the compression mechanism to be used.

If the data being sent or received is already compressed, OpenSSL will compress it a second time. This can happen when already compressed binaries like .gif or .zip are sent, or when the server uses gzip encoding for a http response. This can have impact on performance and memory usage.

Ben Reser adds in the comments:
(Ben is a Full Committer/PMC Member of Apache Subversion project and httpd project)

You can actually end up with up to 3 layers of compression.

The plaintext file may be compressed (user controlled),

the subversion diff format sent over the network can be compressed (controlled via -c for svnserve and SVNCompressionLevel for httpd),

and the on disk repository delta format can be compressed (will be configurable in fsfs.conf in 1.9).
The last bit is known to be a significant drain on compressed file transfer speeds and until 1.9, you can't really do anything about it other than avoiding adding compressed files to SVN.