this all depends on your database.. if you have large fields like the description field as long as like 500 characters.. then with links2 you can get somewhere around 4000 links.. (and links will still run.. but not so well.. much slower..)

links sql.. you will almost never notice a difference with the speed.. you probably will be able to reach a million cause it is SQL.. but an oracle DB can practically handle unlimited but the thing is it costs money.. the thing is that both take diskspace.. if you have a larger db with links2.. you will run into cpu/system resource problems and have a chance of getting your site shutdown by your host..

jerry