the 179 limit is computed on your 1040 not the 1120s. say the S-Corp has a profit before 179 of $30K. 179 is $50K and you took a salary from the S-Corp of $40K. your business income for 179 purposes is the $30K + the salary of $40K giving you business income of $70K which means the 179 would be allowed in full in this example. this is no carryback. another consideration is do you have basis for your actual loss.
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form 7203 was first required for certain 2021 returns
but you might want to use it to see what your basis is for 2019
https://www.irs.gov/pub/irs-prior/f7203--2022.pdf
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there is no business limitation for Special depreciation, but you still need basis to take the loss.
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179 can be more flexible because you can take 0% up to 100%. the remaining cost is deprecation using MACRS and the class life. if you do not take 100% 179 in the first year you cannot take more in ensuing years
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it's really a matter of how you want our taxes to come out subject to any loss restrictions due to basis limitations.
