I’ve been looking over a lot of voltage regulator schematics, and I’ve noticed that a lot of them prefer the MIC29302s, MIC4680 instead of the cheaper LD1117s
MICs (often used)
http://www.digikey.com/product-detail/en/MIC4680-5.0YM%20TR/576-1221-2-ND/771690
(vs cheapo like this one)
Any particular reason for that? Even the Chinese use these.
You are comparing linear to switching regulator. There is huge difference between them. Try googeling it to learn more about the differences please.
the first one is a switch mode regulator, the second is a LDO linear regulator.
A simple power supply design is to use a LDO as it needs the minimum of support passives, but has limitations in how much power it can burn up to regulate your voltage - so doesn’t handle large drops from VIN down to the output voltage.
If you’re doing a switch mode power supply (SMPS) then you need more to surround the supply - usually as a minimum you’ll need an inductor as that’s what is doing the up/down conversion.
So, by looking at your DP design. The 5V uses a switched regulator, the 3v3 doesn’t. After reading about it I would assume this design is because the 5V accepts a much higher input voltage; thus a linear one would generate a lot of heat. The 3v3 is feed of the 5v; since there is such a small difference in voltage not a lot of heat is generated…?
You got it!
I knew my degree in liberal arts would come to good use one day.
Perfect understanding. We got the best of both worlds, 30V input but still low cost 
lol