I am always a fan of longer names. Both [name_m]William[/name_m] and [name_m]Liam[/name_m] are great names. I feel like with your last name [name_m]Liam[/name_m] is the way to go, but as I said, I am a sucker for longer names. When Your son is born, [name_m]Liam[/name_m] can be solely what you call him from the get go nipping the other [name_m]William[/name_m] nicknames out. However, one day down the line he may decides he dislikes the name [name_m]Liam[/name_m], or something may happen making him want to go by something different. Or he may just ‘not be a [name_m]Liam[/name_m]’ as time goes by. A comrade of mine has a young grandson named [name_m]William[/name_m], he was suppose to a [name_m]Liam[/name_m], but it just didn’t fit with his personality, nor did [name_m]Will[/name_m] or [name_m]Willy[/name_m] or [name_m]Bill[/name_m] Ect. His parents had their hearts set on [name_m]Liam[/name_m], and everyone in the family agreed it was “the perfect name”. But after he was born and some time went on, the parents as well as everyone else in the family felt he was not a [name_m]Liam[/name_m]. So his parents started to call him [name_m]William[/name_m] which seemed to suit him much better.
I like the name [name_m]Liam[/name_m], just [name_m]Liam[/name_m], but I guess it’s always nice to keep the options open “just in case”. But either way, you can’t go wrong.