Sandeep,
I think you've touched on most of the relevant issues. - One other issue to consider is whether the blob data is manipulated in the database. - I think that most filesystems can handle that amount of files, but may need a sys admin who knows what they are doing to tune the file system a little. - Storing the blobs on file systems also offers the opportunity to store the blobs on another server, and reduce your Oracle licensing costs. - You shouldn't be building your test and development databases with exp/imp. Clone the database, preferably from a backup, so you actually test your backups occassionally. - Having the blobs on a filesystem can cause additional administrative work, for example when you build the test database, then somebody will have the additional step of copying the files to the test system. - Maybe more programming work as the application is developed. Your developers should be consulted. - In summary, there is no hard-and-fast rule of which is better. Your mileage may vary. You'll just need to examine all the factors and then probably do a benchmark with your data in your environment to come to a conclusion.