If it takes person A 1 month to build the same thing as person B in 2 months, all else being equal, person A has a better shot at succeeding.
Then it's not viable, which is what the V stands for. So it's not an MVP at all, it's just shit.
When it comes to marketing what you've made, you do get the first-mover advantage but that's about all you get.
I've made many a useful, problem-solving prototype in my spare time (and even 'launched' a few of them among close friends and family) only to see the same thing going big a month later. Except, it is someone else who happens to have made the same thing a; they just manage to push it a lot better that I ever could. It also doesn't help that I'm really bad at the business side of things.
I really need to find someone who can do that for me and my ideas/prototypes... :(