I view the main benefits of marriage as:
- Having the wedding day, which is (only to me personally, others may not feel the same) an emotionally and socially significant day, celebrating with family and friends, displaying commitment, creating a treasured memory etc.
- Relating to above, in particular it's something that I know will greatly please my parents (only for the sake of my happiness and getting to go to their child's wedding, not because of controlling expectations) I bit like having a graduation ceremony doesn't make a difference to your degree, but people want to go and feel proud to be there.
- Social benefits, it is my perception that others are more likely to take a married couple more seriously and treat the relationship with more respect. Although granted, I think this aspect is probably greater before you have children / if you don't have children, and is probably gradually changing.
- Legal benefits/ recognition of the relationship. Although I think this is (quite rightly) changing so that long-term cohabiting couples or in some other way "registered" couples will probably have identical rights fairly soon.
- Lastly, and probably leastly - the tradition and the connotations of marriage (commitment, ring-wearing, going through the wedding malarky, "rite of passage", romantic associations) just appeal to me, and are what I have imagined as a "nice thing that will happen one day" for a long time. Although, obviously that appeal might not exist for others and is fairly subjective/meaningless I know, it would just be dishonest not to mention it as a reason.
In direct answer to OPs questions - no I don't think marriage will make much of a difference to me - ultimately a loving relationship is a loving relationship, and marriage doesn't change that. But those are my reasons for wanting to regardless.
I have nothing against unmarried couples (marriage doesn't appeal to everyone and shouldn't have to) and truly believe they should not be discriminated against in any way; but it does irk me when people say "it's stupid to get married", "if you need marriage to validate your relationship you aren't in love" etc - to me that's erroneously jumping to simplified conclusions about why people want to get married, and also in many cases being a hypocrite. Eg: I don't need to go to a graduation ceremony to "validate" my degree, but I still want to, I don't need to have a party to "validate" how old I am, but I like to, having a Sunday roast as a family won't majorly alter your family bonds but for many it is a welcome tradition, we don't need to have funerals to "validate" somebody's passing - but social rituals like these are often beneficial in more subtle ways and are clearly something that in general appeal to human beings (including the "intelligent" and "rational") whatever they mark (or indeed even if they are fairly arbitrary).