I’ve seen [name]Shawn[/name], [name]Shaun[/name], and [name]Sean[/name]. I prefer [name]Sean[/name] because it seems much more classic and I think it is the “original”
I like [name]Sean[/name] better. It’s the traditional Irish spelling. But, I think maybe it depends on who the character is. My brother-in-law is named [name]Shawn[/name]. He does have Irish heritage, but he grew up in the country in Kansas, so I think that spelling works for him.
I automatically think “[name]Sean[/name]” first.
Although, there was a kid in my highschool that spelled it “[name]Shaun[/name]”.
[name]Sean[/name], but I suppose [name]Shawn[/name] would work for a character as well.
Another vote for [name]Sean[/name]
Ugh, it’s honestly a HUGE pet peeve of mine when people butcher the spelling of Irish names.
[name]Sean[/name] to me is the only true spelling, the other two just look so misspelled to me.
[name]Sean[/name] is the original and thus best spelling.
[name]Shaun[/name] and [name]Shawn[/name] are the Anglicized spellings. Out of these two, I prefer [name]Shaun[/name], I think it looks classier than [name]Shawn[/name]. For some reason I’ve always seen the [name]Shawn[/name] spelling as being rather downmarket.
[name]Sean[/name] is my favourite! I’ve only ever met Seans that spelt it that way although I once had class with a girl called Shawyn. Pronounced like [name]Sean[/name]. (why.)
[name]Sean[/name] is the classic version. I prefer that.
I know a [name]Shaun[/name] and a [name]Sean[/name], and [name]Jay[/name]-Zs real name is [name]Shawn[/name].
I prefer the [name]Shawn[/name] spelling.
I prefer [name]Sean[/name], but I’ve only ever met [name]Shawn[/name]'s and [name]Shaun[/name]'s.
[name]Sean[/name], without a doubt.
For a story for me it would depend on the setting. [name]Shawn[/name] looks very '70s-'80s [name]America[/name] to me. [name]Shaun[/name] is kinda hideous at all times [name]IMO[/name] but works for a specific type of character. [name]Sean[/name] is more Irish, and an older spelling. [name]Shane[/name] is a related name that was never as popular in the US and peaked earlier.
Another vote for [name]Sean[/name]
While I like the traditional spelling [name]Sean[/name], I have heard people pronounce it see-in. In fact, I knew a guy named [name]Sean[/name] and it was pronounced see-in. His parents believe that it a legitimate pronunciation. 
I would go with [name]Shawn[/name]. [name]Shaun[/name] and [name]Shon[/name] are kind of odd.
[name]Sean[/name] looks more correct to me, but I would probably use [name]Shawn[/name] or [name]Shaun[/name] myself.
I disagree with the assumption that anglicised Irish names are “made up” or “mispellings”. It’s natural for names from other cultures to be adapted and translated when they enter a new language; [name]Shawn[/name] isn’t any more mispelt than [name]Rory[/name], [name]Alistair[/name], [name]Orla[/name], [name]Aidan[/name], or [name]Maeve[/name] are.
That being said, [name]Sean[/name] looks cleaner and is familiar in the English speaking world so pronunciation wouldn’t be a problem.
They’re both right, along with [name]Shaun[/name].
Personally, I prefer [name]Shawn[/name], but [name]Sean[/name] is correct as well, and so is [name]Shaun[/name].
My first guess would be [name]Sean[/name].
I like [name]Sean[/name] and usually I’m for the “original” spelling of names, but I like [name]Shaun[/name] the best. Mostly because it’s the spelling used for [name]Shaun[/name] of the Dead. 
I also remember having a hard time getting how [name]Sean[/name] was pronounced when I was younger, before I knew about Irish pronunciations. It looked like SEEN to me.