What do you know about the comma used in the sentence with a 'since'? If the structure of a sentence is "Since (Noun + Verb) (Noun + Verb)" How's right?
- Since (Noun + Verb), (Noun + Verb)
- Since (Noun + Verb) (Noun + Verb)
I've found it useful to use a comma because the since clause is a separate qualifying thought/idea:
Since the beginning of time, day will follow night
Since he started running, he's lost weight
It is also a natural place to take a breath when speaking/reading which usually signifies a good place for a comma.
The word "since" is a conjunction introducing a coordinating clause in the structures presented by the OP; "since + subject + verb" forms a subordinating clause.
According to grammar, when a subordinating clause with "since" comes before a main clause, you put a comma after the subordinating clause. So the first structure i.e. "since + noun + verb, noun + verb" is correct, whereas the other structure without comma isn't correct. Look at the following sentences in the first pattern:
Since Adam is going, Peter is going, too.
Since you've finished your homework, you may go out and play.