IMO depends on your age, and the purpose of the relationship.
I mean if you're starting out in life and you are planning a big family and all that, then marriage.

If you've hit the middle age wall so are just ultimately looking for companionship and ego stroking, then at best live in. But really, separate residences would be ideal.

If you're asking "you in particular, would you personally prefer marriage or a live in relationship?"
Then I'd probably say either neither, or maybe marriage due to certain tax and legal benefits.

marriage 100%

To some, marriage is a big deal...it is that affirmation that we are a couple. You get the certificate and you get tax benefits....and you get to call your spouse either your husband or wife. It's traditional.

Now, if you are with someone and you love one another, and you just simply do not want to do the whole marriage thing, then you simply don't do it. Doesn't mean you aren't committed to that person. Some people believe marriage means security and all, and it does. But you can still be with someone, and then have them as your beneficiary, or have a life insurance policy on yourself and them. In the end, it's all up to each couple to decide what they want.

for long terms relationship

legally there is not a great deal of difference ... be sure you understand the term. de facto.. when it applies and what that means for you and your “live-in”

WOW!!!!
YOU PEOPLE ARE REALLY REALLY BAD

Neither!

For me, I'd say neither. I like to live alone.

marriage or nothing

Well here's what I've found: I really like to go out in my yard early in the morning in my sleepwear (usually T shirt & socks) get down on all fours and chase the squirrels and bunnies around.
I've found that sadly most wives just won't put up with this for long.....

live in

Neither at this point. I like keeping my options open. And marriage? Probably never.