This isn't stated correctly: "One benefit in the reimbursement scenario is the favorable effect on reasonable compensation."

Because reimbursement under an accountable plan is Not part of payroll and has no impact on Compensation or taxes. That is the point of An Accountable Plan. It's no different than me buying printer paper on my way to the office; you get the receipt and the paper and Reimburse me. That has nothing to do with Payroll. And if that trip to Staples was out of my way, I decide to also make you pay Mileage for my extra side trip. It's all just repaid to me. Accountable Plan = I proved it to you, so you can just pay me and it isn't part of Payroll.

Here's the issue for this part: "I thought this question to really be an expansion or slight modification of another often approached question pertaining to S-Corps; which is, "should i put vehicle in my name and get reimbursed" or "put vehicle in that of the company". This is a very common question, and we run the cost/benefit of each."

Because any Personal use of that vehicle, such as the Truck is in the name of S Corp 1, and the person uses it for S Corp 2 and for the LLC and for Commuting, makes all of this other use Personal and taxable through Payroll as a Fringe Benefit.

So, for instance, S Corp 1 owns and pays to operate a vehicle. Your Employee of S Corp 1 gets taxed on that value for all the Personal use, all the S Corp 2 use and all the LLC use.

All you are doing is Hiding the marble under a different cup. If I bought a Truck to use for the LLC because I need a Truck to do what I need to do, why would I park it and not use it for other things when I need a Truck to do what I need to do for the other things? That is what you seem to be stating is your advice.