When I write to my friends or say on the phone 会いたいね/また会いたいね, it's like "we haven't seen each other for so long so let's meet up sometime"
but if you just say 「会いたい」 , it might sound like
you have some kind of romantic feelings,
especially when you say it to someone of the opposite sex
In a business situation you might say お会いしたいです, お会いできますか etc.
So I think it depends on the situation and how you say it, like whether you add ね, です, お~したいです etc.