Both Choices Are Acceptable
From a grammatical perspective, you can find just as many "experts" who mandate a comma before the "LLC" in your company's name as those who feel strongly that is should be omitted. Many experts believe a comma should always be included with an "LLC," "Inc." or "Ltd." because these are acronyms, not full words. Conversely, AP style strongly recommends that a comma should not appear before these acronyms. Lacking any universal agreement, both options are acceptable.
LLC Legal Name
The important question involves your LLC's legal name. When you file to register your LLC as a recognized organization in your state, every digit -- whether letter, number or punctuation -- is critical. Your state will approve your company name exactly as written. Therefore, if you include a comma before "LLC" in your name, it will get approval in that format. Omitting a comma will generate approval devoid of punctuation. This result can be important in the future, potentially even creating some risk in certain situations.
Legally-binding contracts are the most important consideration. For example, should your legal LLC name include a comma and you sign a contract without the comma, the new contract may be invalid, as signing an agreement without the punctuation legally represents a different organization. If the contract is fulfilled satisfactorily, the oversight will be meaningless. However, should problems arise, the lack of a comma could become important.
Whichever option you choose, consistency in writing your LLC's name is the critical issue. Whether you decide to include or omit a comma before the "LLC," write your company name the same way every time to avoid facing the necessity of re-registering your company because of a punctuation error. For example, ABC Company, LLC is a different entity than ABC Company LLC. While the difference may appear trivial to you, in the legal universe it can be significant.