Comment by rafeed

Besides offering lossless quality images, JPEGmini allows a much larger file size. Compressor.io only appears to allow 10MB files, which if you're trying to use it for photography, it won't be very useful because the jpeg's produced by a Canon 5D Mark III are about 20MB-30MB in size. It is also only web based, whereas JPEGmini has a native client. Compressor.io looks promising though.