The LL is long life. Same physical bulb with same lumens.
They just run a high quality filament and most likely a higher gas pressure inside the bulb.

 

If you got the LL bulb, there is no real difference. The regular 3157 is 3 times the life (generally 1200 hours versus 400 for the 3457). They are the same base, filiment, amp (LL only, there is a difference in the standard ones), etc.

Xtravision headlights are good ones, they are a little brighter than standard, really long life. I personally like my Silverstars better than the Xtravision, and I have had them for 5 years in my Grand Marquis and they are still working fine. They are a tinted bulb and many don't like them because if that, but I like the white light they output, and I get way less artifacts and dead spots in my car. I have cool blues in my 89, they are okay, but the Xtravision is way better.