Deductions & credits

This is an update: Per your suggestion, to avoid recapture if I retire in a year or three (although I wonder if it completely avoids such), I changed the computers from Section 179 to 100% special depreciation allowance.  It made no change whatsoever to my federal tax bill but a sizable change to my state tax bill.  I assume the latter is because my state (CA) is less liberal on accelerated depreciation/S179.  What I don't understand is why the Federal tax due did not change at all.   To be clear, I am not subject to AMT or anything like that. 

 

Does my choice between the two above, for any of the three items that I could choose one method or the other for, have anything to do with whether the cost of certain items exceed $2,500?

 

Thanks!