LLC & Partnership - W2 vs SE tax

[AZ-Tax]

Its my understanding that a member of a LLC or partner of partnership should not issue a W-2 to its member or partner if not elected to be taxed as a Corp. Is the main reason for this is the LLC or Partnership will deduct 100% of the employee and employers portion of the SS tax on the W-2 opposed to an LLC or Partnership deducting 50% of the SE tax?

Am I correct?

[TaxmannEA]

A partner in a partnership takes guaranteed payments and their share of partnership earnings or loss. As the partnership is not considered to be a separate entity, the partner would be paying himself wages. The partner and partnership also get a small break in the overall rate by paying SE tax as opposed to FICA withholding. (92.35% of income)
That being said, I have seen several sole proprietors and partners use W-2 wages and not be penalized. The SS and Medicare are paid in either way.