What are the major internal differences between the Leupold VX3 and Mark 4 scopes. Do the marks 4's have better glass etc ?

You can try this link and ask them directly. There phone number is 800-LEUPOLD, but I noticed you are not in the USA. Someone else may have your answer.
http://www.leupold.com/corpora...-us/service-support/

Thank you for the link and noticing not everyone lives in the USA.

I'm trying to decide if the price difference is worth it and if it will buy be even more reliability.

I have heard that there are no internal differences between the VX-3 and Mark 4 rifle scopes and that the glass is the same. You might check out the forum at snipershide.com for more discussion on the subject.

I am a Leupold man and believe in their products, but I think you'll find the main difference is the marketing buzzword "tactical". It's the new "short mag" and you know you can't have a super duper black rifle w/o a "tactical" scope. It just wouldn't be right.