I'd says this depends on ones state at the time of the marriage. I personally only married the first time out of a sense of duty. I didn't love him. Since we'd never been allowed to be alone together, I didn't even really know him. When I left, I didn't feel like I'd really broken a bond with him. He wasn't right for me. I wasn't right for him. I honestly just wanted a way out of my house.
I am married now & it doesn't feel like the second time for me. My heart was never in the first one. My commitment to my husband feels like a real one now. The paper and ceremony were really just a celebration of our love. I'd already chosen him in my heart. To me that is the difference.
However, many JWs do marry for love. Some even leave together and still consider themselves married. There is not a problem with that. I'm sure that some even choose to renew their vows within their new religion to make their new relationship with god a part of their marriage.
I suppose I'd say the same about baptism as well. When I was baptized, I did it to be allowed to date my now ex-husband. I didn't say the prayer beforehand like I was supposed to. I didn't even respond when they asked the questions. I just stood in line and got dunked. I do not consider myself to be baptized at all. If I belived in god and wanted to join a church, I would be baptized properly.