Differences between de minimis safe harbor election and section 179 (& when you *wouldn't* take it)?

Regarding the de minimis safe harbor election:

1) I understand that its purpose is to allow you to enter items up to $2500 as an expense rather than asset.  In other words, $2500 is the dollar value *up to which* it can be used to expense items.  But what's the dollar value *from which* it becomes relevant?  For instance, even without taking this, smaller items like $50 can already be expensed.  So then, at what point must you take this election in order to be allowed to expense something?  If an item is $100, can you just expense it without taking the election?  What about $200?  etc.

2) According to this question (https://ttlc.intuit.com/questions/3146193-when-they-say-if-you-take-the-de-minimis-safe-harbor-elect...), I understand that even if you take the election, you can still choose to enter each item as an asset if you wish.  So if you don't take it, items between $? and $2500 must be entered as assets - but if you do, they can either be assets or expenses.  But if that's true...why would anyone not take it, if you can just choose to enter things as assets anyway?  The interview specifically mentions that "once you make your election for your return, it will be very complicated to undo it if you change your mind" - but offers no information about what ramifications might result from taking it (in terms of what reason could there possibly be for wanting to undo it)?

3) The election allows you to expense items, thereby getting the full tax benefit this year.  Entering assets as section 179 asset does the same.  So...what benefit does this offer?  Why not just enter items as 179 assets, thereby getting the same tax benefit this year (of getting the full 'value' of the writeoff this year)?  It's the same result, no?