john-laurens:

ciceroprofacto:

I’ve actually thought about this a lot and my leaning is toward the second.

John was characteristically more blunt about things when he was sure of what he was saying. His actions on the battlefield, his statements during Lee’s court-martial, his behavior as a minister in France and his persistence on the black battalion- pretty much everything he does during the revolution is very straightforward, especially when his feelings or his resolve are called into question.
John also wrote considerably less in quantity than Alex did- which Alexander complained about (though he did that with everyone). But, Alex never implied that John’s letters failed to convey his feelings, and besides feeling neglected in quantity, Alex- characteristically a guarded person who did not trust (much less love) easily, was satisfied with the message John got across.

Alex was comparatively self-preserving. Even when he extended vulnerability as he did with Kitty Livingston, he was logical about the timing and his objectives. In accounts from his friends, describing him before he met Laurens, he never comes across as vain-glorious or belligerent (wouldn’t help him to be). Laurens comes across as the louder personality in that regard, and could afford to be. Hamilton was, by necessity, more diplomatic.
Alex was also very talented with conveying meaning with innuendo. It’s one thing to use words well, but another to use them in a way that specific people will understand. This was part of his usefulness to Washington.

So, I don’t think it would make sense for John’s letters not to be just as- if not more- overtly affectionate. John wouldn’t have liked to write without feeling, and Alex would have felt worried or insecure if John’s writings came across cold. Even if John wasn’t as talented with words, I’m sure he was using his own bawdy innuendo to get across his own feelings- probably in a characteristically blunt way.
And, keep in mind we’re missing many of their letters- I think it’s telling which ones remain. I think Alex definitely destroyed most of John’s letters and I think John gave him very good reason to.

tldr; between the two of them- as far as recklessness goes- Alex might’ve dared to write the April ‘79 letter, but John dared to keep it. 
He would probably do a lot worse himself.

I also have a post here that discusses some of the problems with directly comparing the volume of letters written by Hamilton or Laurens or comparing the language contained within those surviving letters.  We don’t have all the letters that existed between those two, so we shouldn’t assume that lack of evidence is evidence of a lack (of affection, of love, of commitment, etc.).  @ciceroprofacto raises a good point in stating that we don’t have many of the letters that Laurens sent to Hamilton – and it certainly seems possible (if not likely) that those lost letters contained some of Laurens’s more sexual or bawdy writings.