The standard mileage rate includes depreciation (about 25 cents of the 59 cents is for depreciation). So you can never use the standard mileage rate and claim depreciation on the same vehicle. If you take section 179, then you can also deduct actual expenses (fuel, repairs, insurance--but NOT depreciation). Deducting actual expenses requires more effort and record keeping on your part. See chapter 4 of publication 463,
https://www.irs.gov/forms-pubs/about-publication-463
Depending on your expected use, the vehicle cost, and how long you plan to keep the car, the standard rate can give you a bigger long term deduction, because you can keep claiming the standard rate (which includes depreciation) long after the vehicle is fully depreciated.
Example: Joe buys a used car for $2500 to use for ride share and delivery. He drives 10000 miles per year and claims the standard mileage rate. At the end of the first year, the car is fully depreciated (25 cents per mile x 10,000 miles = $2500), but if Joe keeps driving the same car, he will continue to claim a deduction for depreciation even though the car is fully depreciated. This is perfectly legal and does not require any tax adjustments or payback.
On the other hand, if you prefer to change vehicles frequently and you buy expensive new vehicles, you may want to depreciate and then use the actual expense method for other expenses. There's no right answer for everyone.
